Merge bd595c0429 into 85f96b01b7

src/CMakeLists.txt

@@ -38,7 +38,7 @@ message("Configuring secp256k1 subtree...")
 set(SECP256K1_DISABLE_SHARED ON CACHE BOOL "" FORCE)
 set(SECP256K1_ENABLE_MODULE_ECDH OFF CACHE BOOL "" FORCE)
 set(SECP256K1_ENABLE_MODULE_RECOVERY ON CACHE BOOL "" FORCE)
-set(SECP256K1_ENABLE_MODULE_MUSIG OFF CACHE BOOL "" FORCE)
+set(SECP256K1_ENABLE_MODULE_MUSIG ON CACHE BOOL "" FORCE)
 set(SECP256K1_BUILD_BENCHMARK OFF CACHE BOOL "" FORCE)
 set(SECP256K1_BUILD_TESTS ${BUILD_TESTS} CACHE BOOL "" FORCE)
 set(SECP256K1_BUILD_EXHAUSTIVE_TESTS ${BUILD_TESTS} CACHE BOOL "" FORCE)
@@ -136,6 +136,7 @@ add_library(bitcoin_common STATIC EXCLUDE_FROM_ALL
   key.cpp
   key_io.cpp
   merkleblock.cpp
+  musig.cpp
   net_permissions.cpp
   net_types.cpp
   netaddress.cpp

src/common/messages.cpp

@@ -116,6 +116,10 @@ bilingual_str PSBTErrorString(PSBTError err)
             return Untranslated("External signer failed to sign");
         case PSBTError::UNSUPPORTED:
             return Untranslated("Signer does not support PSBT");
+        case PSBTError::INCOMPLETE:
+            return Untranslated("Input needs additional signatures or other data");
+        case PSBTError::OK:
+            return Untranslated("No errors");
         // no default case, so the compiler can warn about missing cases
     }
     assert(false);

src/common/types.h

@@ -20,6 +20,8 @@ enum class PSBTError {
     EXTERNAL_SIGNER_NOT_FOUND,
     EXTERNAL_SIGNER_FAILED,
     UNSUPPORTED,
+    INCOMPLETE,
+    OK,
 };
 } // namespace common
 

src/interfaces/wallet.h

@@ -207,7 +207,7 @@ public:
         int& num_blocks) = 0;
 
     //! Fill PSBT.
-    virtual std::optional<common::PSBTError> fillPSBT(int sighash_type,
+    virtual std::optional<common::PSBTError> fillPSBT(std::optional<int> sighash_type,
         bool sign,
         bool bip32derivs,
         size_t* n_signed,

src/key.cpp

@@ -13,6 +13,7 @@
 #include <secp256k1.h>
 #include <secp256k1_ellswift.h>
 #include <secp256k1_extrakeys.h>
+#include <secp256k1_musig.h>
 #include <secp256k1_recovery.h>
 #include <secp256k1_schnorrsig.h>
 
@@ -349,6 +350,127 @@ KeyPair CKey::ComputeKeyPair(const uint256* merkle_root) const
     return KeyPair(*this, merkle_root);
 }
 
+std::vector<uint8_t> CKey::CreateMuSig2Nonce(MuSig2SecNonce& secnonce, const uint256& hash, const CPubKey& aggregate_pubkey, const std::vector<CPubKey>& pubkeys)
+{
+    // Get the keyagg cache and aggregate pubkey
+    secp256k1_musig_keyagg_cache keyagg_cache;
+    if (!GetMuSig2KeyAggCache(pubkeys, keyagg_cache)) return {};
+    std::optional<CPubKey> agg_key = GetCPubKeyFromMuSig2KeyAggCache(keyagg_cache);
+    if (!agg_key.has_value()) return {};
+    if (aggregate_pubkey != *agg_key) return {};
+
+    // Parse participant pubkey
+    CPubKey our_pubkey = GetPubKey();
+    secp256k1_pubkey pubkey;
+    if (!secp256k1_ec_pubkey_parse(secp256k1_context_sign, &pubkey, our_pubkey.data(), our_pubkey.size())) {
+        return {};
+    }
+
+    // Generate randomness for nonce
+    uint256 rand;
+    GetStrongRandBytes(rand);
+
+    // Generate nonce
+    secp256k1_musig_pubnonce pubnonce;
+    if (!secp256k1_musig_nonce_gen(secp256k1_context_sign, secnonce.Get(), &pubnonce, rand.data(), UCharCast(begin()), &pubkey, hash.data(), &keyagg_cache, nullptr)) {
+        return {};
+    }
+
+    // Serialize nonce
+    std::vector<uint8_t> out;
+    out.resize(66);
+    if (!secp256k1_musig_pubnonce_serialize(secp256k1_context_sign, out.data(), &pubnonce)) {
+        return {};
+    }
+
+    return out;
+}
+
+std::optional<uint256> CKey::CreateMuSig2PartialSig(const uint256& hash, const CPubKey& aggregate_pubkey, const std::vector<CPubKey>& pubkeys, const std::map<CPubKey, std::vector<uint8_t>>& pubnonces, MuSig2SecNonce& secnonce, const std::vector<std::pair<uint256, bool>>& tweaks)
+{
+    secp256k1_keypair keypair;
+    if (!secp256k1_keypair_create(secp256k1_context_sign, &keypair, UCharCast(begin()))) return std::nullopt;
+
+    // Get the keyagg cache and aggregate pubkey
+    secp256k1_musig_keyagg_cache keyagg_cache;
+    if (!GetMuSig2KeyAggCache(pubkeys, keyagg_cache)) return std::nullopt;
+    std::optional<CPubKey> agg_key = GetCPubKeyFromMuSig2KeyAggCache(keyagg_cache);
+    if (!agg_key.has_value()) return std::nullopt;
+    if (aggregate_pubkey != *agg_key) return std::nullopt;
+
+    // Parse the pubnonces
+    std::vector<std::pair<secp256k1_pubkey, secp256k1_musig_pubnonce>> signers_data;
+    std::vector<const secp256k1_musig_pubnonce*> pubnonce_ptrs;
+    size_t ours = 0;
+    CPubKey our_pubkey = GetPubKey();
+    for (const CPubKey& part_pk : pubkeys) {
+        const auto& pn_it = pubnonces.find(part_pk);
+        if (pn_it == pubnonces.end()) return std::nullopt;
+        const std::vector<uint8_t> pubnonce = pn_it->second;
+        if (pubnonce.size() != 66) return std::nullopt;
+        if (part_pk == our_pubkey) {
+            ours = signers_data.size();
+        }
+
+        auto& [secp_pk, secp_pn] = signers_data.emplace_back();
+
+        if (!secp256k1_ec_pubkey_parse(secp256k1_context_sign, &secp_pk, part_pk.data(), part_pk.size())) {
+            return std::nullopt;
+        }
+
+        if (!secp256k1_musig_pubnonce_parse(secp256k1_context_sign, &secp_pn, pubnonce.data())) {
+            return std::nullopt;
+        }
+    }
+    pubnonce_ptrs.reserve(signers_data.size());
+    for (auto& [_, pn] : signers_data) {
+        pubnonce_ptrs.push_back(&pn);
+    }
+
+    // Aggregate nonces
+    secp256k1_musig_aggnonce aggnonce;
+    if (!secp256k1_musig_nonce_agg(secp256k1_context_sign, &aggnonce, pubnonce_ptrs.data(), pubnonce_ptrs.size())) {
+        return std::nullopt;
+    }
+
+    // Apply tweaks
+    for (const auto& [tweak, xonly] : tweaks) {
+        if (xonly) {
+            if (!secp256k1_musig_pubkey_xonly_tweak_add(secp256k1_context_static, nullptr, &keyagg_cache, tweak.data())) {
+                return std::nullopt;
+            }
+        } else if (!secp256k1_musig_pubkey_ec_tweak_add(secp256k1_context_static, nullptr, &keyagg_cache, tweak.data())) {
+            return std::nullopt;
+        }
+    }
+
+    // Create musig_session
+    secp256k1_musig_session session;
+    if (!secp256k1_musig_nonce_process(secp256k1_context_sign, &session, &aggnonce, hash.data(), &keyagg_cache)) {
+        return std::nullopt;
+    }
+
+    // Create partial signature
+    secp256k1_musig_partial_sig psig;
+    if (!secp256k1_musig_partial_sign(secp256k1_context_sign, &psig, secnonce.Get(), &keypair, &keyagg_cache, &session)) {
+        return std::nullopt;
+    }
+    secnonce.Invalidate();
+
+    // Verify partial signature
+    if (!secp256k1_musig_partial_sig_verify(secp256k1_context_sign, &psig, &(signers_data.at(ours).second), &(signers_data.at(ours).first), &keyagg_cache, &session)) {
+        return std::nullopt;
+    }
+
+    // Serialize
+    uint256 sig;
+    if (!secp256k1_musig_partial_sig_serialize(secp256k1_context_sign, sig.data(), &psig)) {
+        return std::nullopt;
+    }
+
+    return sig;
+}
+
 CKey GenerateRandomKey(bool compressed) noexcept
 {
     CKey key;

src/key.h

@@ -7,6 +7,7 @@
 #ifndef BITCOIN_KEY_H
 #define BITCOIN_KEY_H
 
+#include <musig.h>
 #include <pubkey.h>
 #include <serialize.h>
 #include <support/allocators/secure.h>
@@ -220,6 +221,9 @@ public:
      *                               Merkle root of the script tree).
      */
     KeyPair ComputeKeyPair(const uint256* merkle_root) const;
+
+    std::vector<uint8_t> CreateMuSig2Nonce(MuSig2SecNonce& secnonce, const uint256& hash, const CPubKey& aggregate_pubkey, const std::vector<CPubKey>& pubkeys);
+    std::optional<uint256> CreateMuSig2PartialSig(const uint256& hash, const CPubKey& aggregate_pubkey, const std::vector<CPubKey>& pubkeys, const std::map<CPubKey, std::vector<uint8_t>>& pubnonces, MuSig2SecNonce& secnonce, const std::vector<std::pair<uint256, bool>>& tweaks);
 };
 
 CKey GenerateRandomKey(bool compressed = true) noexcept;

src/musig.cpp

@@ -0,0 +1,183 @@
+// Copyright (c) 2024-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <musig.h>
+#include <support/allocators/secure.h>
+
+#include <secp256k1_musig.h>
+
+bool GetMuSig2KeyAggCache(const std::vector<CPubKey>& pubkeys, secp256k1_musig_keyagg_cache& keyagg_cache)
+{
+    // Parse the pubkeys
+    std::vector<secp256k1_pubkey> secp_pubkeys;
+    std::vector<const secp256k1_pubkey*> pubkey_ptrs;
+    for (const CPubKey& pubkey : pubkeys) {
+        if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &secp_pubkeys.emplace_back(), pubkey.data(), pubkey.size())) {
+            return false;
+        }
+    }
+    pubkey_ptrs.reserve(secp_pubkeys.size());
+    for (const secp256k1_pubkey& p : secp_pubkeys) {
+        pubkey_ptrs.push_back(&p);
+    }
+
+    // Aggregate the pubkey
+    if (!secp256k1_musig_pubkey_agg(secp256k1_context_static, nullptr, &keyagg_cache, pubkey_ptrs.data(), pubkey_ptrs.size())) {
+        return false;
+    }
+    return true;
+}
+
+std::optional<CPubKey> GetCPubKeyFromMuSig2KeyAggCache(secp256k1_musig_keyagg_cache& keyagg_cache)
+{
+    // Get the plain aggregated pubkey
+    secp256k1_pubkey agg_pubkey;
+    if (!secp256k1_musig_pubkey_get(secp256k1_context_static, &agg_pubkey, &keyagg_cache)) {
+        return std::nullopt;
+    }
+
+    // Turn into CPubKey
+    unsigned char ser_agg_pubkey[CPubKey::COMPRESSED_SIZE];
+    size_t ser_agg_pubkey_len = CPubKey::COMPRESSED_SIZE;
+    secp256k1_ec_pubkey_serialize(secp256k1_context_static, ser_agg_pubkey, &ser_agg_pubkey_len, &agg_pubkey, SECP256K1_EC_COMPRESSED);
+    return CPubKey(ser_agg_pubkey, ser_agg_pubkey + ser_agg_pubkey_len);
+}
+
+std::optional<CPubKey> MuSig2AggregatePubkeys(const std::vector<CPubKey>& pubkeys)
+{
+    secp256k1_musig_keyagg_cache keyagg_cache;
+    if (!GetMuSig2KeyAggCache(pubkeys, keyagg_cache)) {
+        return std::nullopt;
+    }
+    return GetCPubKeyFromMuSig2KeyAggCache(keyagg_cache);
+}
+
+class MuSig2SecNonceImpl
+{
+private:
+    //! The actual secnonce itself
+    secure_unique_ptr<secp256k1_musig_secnonce> m_nonce;
+
+public:
+    MuSig2SecNonceImpl() : m_nonce{make_secure_unique<secp256k1_musig_secnonce>()} {}
+
+    // Delete copy constructors
+    MuSig2SecNonceImpl(const MuSig2SecNonceImpl&) = delete;
+    MuSig2SecNonceImpl& operator=(const MuSig2SecNonceImpl&) = delete;
+
+    secp256k1_musig_secnonce* Get() const { return m_nonce.get(); }
+    void Invalidate() { m_nonce.reset(); }
+    bool IsValid() { return m_nonce != nullptr; }
+};
+
+MuSig2SecNonce::MuSig2SecNonce() : m_impl{std::make_unique<MuSig2SecNonceImpl>()} {}
+
+MuSig2SecNonce::MuSig2SecNonce(MuSig2SecNonce&&) noexcept = default;
+MuSig2SecNonce& MuSig2SecNonce::operator=(MuSig2SecNonce&&) noexcept = default;
+
+MuSig2SecNonce::~MuSig2SecNonce() = default;
+
+secp256k1_musig_secnonce* MuSig2SecNonce::Get() const
+{
+    return m_impl->Get();
+}
+
+void MuSig2SecNonce::Invalidate()
+{
+    return m_impl->Invalidate();
+}
+
+bool MuSig2SecNonce::IsValid()
+{
+    return m_impl->IsValid();
+}
+
+std::optional<std::vector<uint8_t>> CreateMuSig2AggregateSig(const std::vector<CPubKey>& participants, const CPubKey& aggregate_pubkey, const std::vector<std::pair<uint256, bool>>& tweaks, const uint256& sighash, const std::map<CPubKey, std::vector<uint8_t>>& pubnonces, const std::map<CPubKey, uint256>& partial_sigs)
+{
+    if (!participants.size()) return std::nullopt;
+
+    // Get the keyagg cache and aggregate pubkey
+    secp256k1_musig_keyagg_cache keyagg_cache;
+    if (!GetMuSig2KeyAggCache(participants, keyagg_cache)) return std::nullopt;
+    std::optional<CPubKey> agg_key = GetCPubKeyFromMuSig2KeyAggCache(keyagg_cache);
+    if (!agg_key.has_value()) return std::nullopt;
+    if (aggregate_pubkey != *agg_key) return std::nullopt;
+
+    // Check if enough pubnonces and partial sigs
+    if (pubnonces.size() != participants.size()) return std::nullopt;
+    if (partial_sigs.size() != participants.size()) return std::nullopt;
+
+    // Parse the pubnonces and partial sigs
+    std::vector<std::tuple<secp256k1_pubkey, secp256k1_musig_pubnonce, secp256k1_musig_partial_sig>> signers_data;
+    std::vector<const secp256k1_musig_pubnonce*> pubnonce_ptrs;
+    std::vector<const secp256k1_musig_partial_sig*> partial_sig_ptrs;
+    for (const CPubKey& part_pk : participants) {
+        const auto& pn_it = pubnonces.find(part_pk);
+        if (pn_it == pubnonces.end()) return std::nullopt;
+        const std::vector<uint8_t> pubnonce = pn_it->second;
+        if (pubnonce.size() != 66) return std::nullopt;
+        const auto& it = partial_sigs.find(part_pk);
+        if (it == partial_sigs.end()) return std::nullopt;
+        const uint256& partial_sig = it->second;
+
+        auto& [secp_pk, secp_pn, secp_ps] = signers_data.emplace_back();
+
+        if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &secp_pk, part_pk.data(), part_pk.size())) {
+            return std::nullopt;
+        }
+
+        if (!secp256k1_musig_pubnonce_parse(secp256k1_context_static, &secp_pn, pubnonce.data())) {
+            return std::nullopt;
+        }
+
+        if (!secp256k1_musig_partial_sig_parse(secp256k1_context_static, &secp_ps, partial_sig.data())) {
+            return std::nullopt;
+        }
+    }
+    pubnonce_ptrs.reserve(signers_data.size());
+    partial_sig_ptrs.reserve(signers_data.size());
+    for (auto& [_, pn, ps] : signers_data) {
+        pubnonce_ptrs.push_back(&pn);
+        partial_sig_ptrs.push_back(&ps);
+    }
+
+    // Aggregate nonces
+    secp256k1_musig_aggnonce aggnonce;
+    if (!secp256k1_musig_nonce_agg(secp256k1_context_static, &aggnonce, pubnonce_ptrs.data(), pubnonce_ptrs.size())) {
+        return std::nullopt;
+    }
+
+    // Apply tweaks
+    for (const auto& [tweak, xonly] : tweaks) {
+        if (xonly) {
+            if (!secp256k1_musig_pubkey_xonly_tweak_add(secp256k1_context_static, nullptr, &keyagg_cache, tweak.data())) {
+                return std::nullopt;
+            }
+        } else if (!secp256k1_musig_pubkey_ec_tweak_add(secp256k1_context_static, nullptr, &keyagg_cache, tweak.data())) {
+            return std::nullopt;
+        }
+    }
+
+    // Create musig_session
+    secp256k1_musig_session session;
+    if (!secp256k1_musig_nonce_process(secp256k1_context_static, &session, &aggnonce, sighash.data(), &keyagg_cache)) {
+        return std::nullopt;
+    }
+
+    // Verify partial sigs
+    for (const auto& [pk, pb, ps] : signers_data) {
+        if (!secp256k1_musig_partial_sig_verify(secp256k1_context_static, &ps, &pb, &pk, &keyagg_cache, &session)) {
+            return std::nullopt;
+        }
+    }
+
+    // Aggregate partial sigs
+    std::vector<uint8_t> sig;
+    sig.resize(64);
+    if (!secp256k1_musig_partial_sig_agg(secp256k1_context_static, sig.data(), &session, partial_sig_ptrs.data(), partial_sig_ptrs.size())) {
+        return std::nullopt;
+    }
+
+    return sig;
+}

src/musig.h

@@ -0,0 +1,54 @@
+// Copyright (c) 2024-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_MUSIG_H
+#define BITCOIN_MUSIG_H
+
+#include <pubkey.h>
+
+#include <vector>
+
+struct secp256k1_musig_keyagg_cache;
+
+class MuSig2SecNonceImpl;
+struct secp256k1_musig_secnonce;
+
+bool GetMuSig2KeyAggCache(const std::vector<CPubKey>& pubkeys, secp256k1_musig_keyagg_cache& keyagg_cache);
+std::optional<CPubKey> GetCPubKeyFromMuSig2KeyAggCache(secp256k1_musig_keyagg_cache& cache);
+std::optional<CPubKey> MuSig2AggregatePubkeys(const std::vector<CPubKey>& pubkeys);
+
+/**
+ * MuSig2SecNonce encapsulates a secret nonce in use in a MuSig2 signing session.
+ * Since this nonce persists outside of libsecp256k1 signing code, we must handle
+ * its construction and destruction ourselves.
+ * The secret nonce must be kept a secret, otherwise the private key may be leaked.
+ * As such, it needs to be treated in the same way that CKeys are treated.
+ * So this class handles the secure allocation of the secp25k1_musig_secnonce object
+ * that libsecp256k1 uses, and only gives out references to this object to avoid
+ * any possibility of copies being made. Furthermore, objects of this class are not
+ * copyable to avoid nonce reuse.
+*/
+class MuSig2SecNonce
+{
+private:
+    std::unique_ptr<MuSig2SecNonceImpl> m_impl;
+
+public:
+    MuSig2SecNonce();
+    MuSig2SecNonce(MuSig2SecNonce&&) noexcept;
+    MuSig2SecNonce& operator=(MuSig2SecNonce&&) noexcept;
+    ~MuSig2SecNonce();
+
+    // Delete copy constructors
+    MuSig2SecNonce(const MuSig2SecNonce&) = delete;
+    MuSig2SecNonce& operator=(const MuSig2SecNonce&) = delete;
+
+    secp256k1_musig_secnonce* Get() const;
+    void Invalidate();
+    bool IsValid();
+};
+
+std::optional<std::vector<uint8_t>> CreateMuSig2AggregateSig(const std::vector<CPubKey>& participants, const CPubKey& aggregate_pubkey, const std::vector<std::pair<uint256, bool>>& tweaks, const uint256& sighash, const std::map<CPubKey, std::vector<uint8_t>>& pubnonces, const std::map<CPubKey, uint256>& partial_sigs);
+
+#endif // BITCOIN_MUSIG_H

src/node/psbt.cpp

@@ -64,7 +64,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
 
             // Figure out what is missing
             SignatureData outdata;
-            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, 1, &outdata);
+            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, std::nullopt, &outdata) == PSBTError::OK;
 
             // Things are missing
             if (!complete) {
@@ -124,7 +124,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
             PSBTInput& input = psbtx.inputs[i];
             Coin newcoin;
 
-            if (!SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, nullptr, 1) || !psbtx.GetInputUTXO(newcoin.out, i)) {
+            if (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, nullptr, std::nullopt) != PSBTError::OK || !psbtx.GetInputUTXO(newcoin.out, i)) {
                 success = false;
                 break;
             } else {

src/psbt.cpp

@@ -4,12 +4,15 @@
 
 #include <psbt.h>
 
+#include <common/types.h>
 #include <node/types.h>
 #include <policy/policy.h>
 #include <script/signingprovider.h>
 #include <util/check.h>
 #include <util/strencodings.h>
 
+using common::PSBTError;
+
 PartiallySignedTransaction::PartiallySignedTransaction(const CMutableTransaction& tx) : tx(tx)
 {
     inputs.resize(tx.vin.size());
@@ -146,6 +149,9 @@ void PSBTInput::FillSignatureData(SignatureData& sigdata) const
     for (const auto& [hash, preimage] : hash256_preimages) {
         sigdata.hash256_preimages.emplace(std::vector<unsigned char>(hash.begin(), hash.end()), preimage);
     }
+    sigdata.musig2_pubkeys.insert(m_musig2_participants.begin(), m_musig2_participants.end());
+    sigdata.musig2_pubnonces.insert(m_musig2_pubnonces.begin(), m_musig2_pubnonces.end());
+    sigdata.musig2_partial_sigs.insert(m_musig2_partial_sigs.begin(), m_musig2_partial_sigs.end());
 }
 
 void PSBTInput::FromSignatureData(const SignatureData& sigdata)
@@ -193,6 +199,13 @@ void PSBTInput::FromSignatureData(const SignatureData& sigdata)
     for (const auto& [pubkey, leaf_origin] : sigdata.taproot_misc_pubkeys) {
         m_tap_bip32_paths.emplace(pubkey, leaf_origin);
     }
+    m_musig2_participants.insert(sigdata.musig2_pubkeys.begin(), sigdata.musig2_pubkeys.end());
+    for (const auto& [agg_key_lh, pubnonces] : sigdata.musig2_pubnonces) {
+        m_musig2_pubnonces[agg_key_lh].insert(pubnonces.begin(), pubnonces.end());
+    }
+    for (const auto& [agg_key_lh, psigs] : sigdata.musig2_partial_sigs) {
+        m_musig2_partial_sigs[agg_key_lh].insert(psigs.begin(), psigs.end());
+    }
 }
 
 void PSBTInput::Merge(const PSBTInput& input)
@@ -220,6 +233,13 @@ void PSBTInput::Merge(const PSBTInput& input)
     if (m_tap_key_sig.empty() && !input.m_tap_key_sig.empty()) m_tap_key_sig = input.m_tap_key_sig;
     if (m_tap_internal_key.IsNull() && !input.m_tap_internal_key.IsNull()) m_tap_internal_key = input.m_tap_internal_key;
     if (m_tap_merkle_root.IsNull() && !input.m_tap_merkle_root.IsNull()) m_tap_merkle_root = input.m_tap_merkle_root;
+    m_musig2_participants.insert(input.m_musig2_participants.begin(), input.m_musig2_participants.end());
+    for (const auto& [agg_key_lh, pubnonces] : input.m_musig2_pubnonces) {
+        m_musig2_pubnonces[agg_key_lh].insert(pubnonces.begin(), pubnonces.end());
+    }
+    for (const auto& [agg_key_lh, psigs] : input.m_musig2_partial_sigs) {
+        m_musig2_partial_sigs[agg_key_lh].insert(psigs.begin(), psigs.end());
+    }
 }
 
 void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
@@ -249,6 +269,7 @@ void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
         sigdata.taproot_misc_pubkeys.emplace(pubkey, leaf_origin);
         sigdata.tap_pubkeys.emplace(Hash160(pubkey), pubkey);
     }
+    sigdata.musig2_pubkeys.insert(m_musig2_participants.begin(), m_musig2_participants.end());
 }
 
 void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
@@ -271,6 +292,7 @@ void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
     for (const auto& [pubkey, leaf_origin] : sigdata.taproot_misc_pubkeys) {
         m_tap_bip32_paths.emplace(pubkey, leaf_origin);
     }
+    m_musig2_participants.insert(sigdata.musig2_pubkeys.begin(), sigdata.musig2_pubkeys.end());
 }
 
 bool PSBTOutput::IsNull() const
@@ -288,6 +310,7 @@ void PSBTOutput::Merge(const PSBTOutput& output)
     if (witness_script.empty() && !output.witness_script.empty()) witness_script = output.witness_script;
     if (m_tap_internal_key.IsNull() && !output.m_tap_internal_key.IsNull()) m_tap_internal_key = output.m_tap_internal_key;
     if (m_tap_tree.empty() && !output.m_tap_tree.empty()) m_tap_tree = output.m_tap_tree;
+    m_musig2_participants.insert(output.m_musig2_participants.begin(), output.m_musig2_participants.end());
 }
 
 bool PSBTInputSigned(const PSBTInput& input)
@@ -372,13 +395,13 @@ PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction&
     return txdata;
 }
 
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash,  SignatureData* out_sigdata, bool finalize)
+PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, std::optional<int> sighash,  SignatureData* out_sigdata, bool finalize)
 {
     PSBTInput& input = psbt.inputs.at(index);
     const CMutableTransaction& tx = *psbt.tx;
 
     if (PSBTInputSignedAndVerified(psbt, index, txdata)) {
-        return true;
+        return PSBTError::OK;
     }
 
     // Fill SignatureData with input info
@@ -393,10 +416,10 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
         // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
         COutPoint prevout = tx.vin[index].prevout;
         if (prevout.n >= input.non_witness_utxo->vout.size()) {
-            return false;
+            return PSBTError::MISSING_INPUTS;
         }
         if (input.non_witness_utxo->GetHash() != prevout.hash) {
-            return false;
+            return PSBTError::MISSING_INPUTS;
         }
         utxo = input.non_witness_utxo->vout[prevout.n];
     } else if (!input.witness_utxo.IsNull()) {
@@ -407,19 +430,38 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
         // a witness signature in this situation.
         require_witness_sig = true;
     } else {
-        return false;
+        return PSBTError::MISSING_INPUTS;
     }
 
+    // Get the sighash type
+    // If both the field and the paramter are provided, they must match
+    // If only the psbt field is provided, refuse to sign. For user safety, the desired sighash must
+    // be provided if the PSBT wants something other than DEFAULT
+    // If only the paramter is provider, use it and add it to the PSBT if it is other than SIGHASH_DEFAULT
+    // for all input types, and not SIGHASH_ALL for non-taproot input types.
+    // If neither are provided, use SIGHASH_DEFAULT
+    if (!sighash) sighash = utxo.scriptPubKey.IsPayToTaproot() ? SIGHASH_DEFAULT : SIGHASH_ALL;
+    if (input.sighash_type && input.sighash_type != sighash) {
+        return PSBTError::SIGHASH_MISMATCH;
+    } else {
+        if ((!utxo.scriptPubKey.IsPayToTaproot() && (sighash != SIGHASH_ALL && sighash != SIGHASH_DEFAULT)) ||
+            (utxo.scriptPubKey.IsPayToTaproot() && sighash != SIGHASH_DEFAULT)
+        ) {
+            input.sighash_type = sighash;
+        }
+    }
+    Assert(sighash.has_value());
+
     sigdata.witness = false;
     bool sig_complete;
     if (txdata == nullptr) {
         sig_complete = ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, utxo.scriptPubKey, sigdata);
     } else {
-        MutableTransactionSignatureCreator creator(tx, index, utxo.nValue, txdata, sighash);
+        MutableTransactionSignatureCreator creator(tx, index, utxo.nValue, txdata, *sighash);
         sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
     }
     // Verify that a witness signature was produced in case one was required.
-    if (require_witness_sig && !sigdata.witness) return false;
+    if (require_witness_sig && !sigdata.witness) return PSBTError::INCOMPLETE;
 
     // If we are not finalizing, set sigdata.complete to false to not set the scriptWitness
     if (!finalize && sigdata.complete) sigdata.complete = false;
@@ -442,13 +484,11 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
         out_sigdata->missing_witness_script = sigdata.missing_witness_script;
     }
 
-    return sig_complete;
+    return sig_complete ? PSBTError::OK : PSBTError::INCOMPLETE;
 }
 
-void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx, const int& sighash_type)
+void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx)
 {
-    // Only drop non_witness_utxos if sighash_type != SIGHASH_ANYONECANPAY
-    if ((sighash_type & 0x80) != SIGHASH_ANYONECANPAY) {
     // Figure out if any non_witness_utxos should be dropped
     std::vector<unsigned int> to_drop;
     for (unsigned int i = 0; i < psbtx.inputs.size(); ++i) {
@@ -465,6 +505,14 @@ void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx, const int&
             to_drop.clear();
             break;
         }
+        // non_witness_utxos can only be dropped if the sighash type does not include SIGHASH_ANYONECANPAY
+        // Since callers should have called SignPSBTInput which updates the sighash type in the PSBT, we only
+        // need to look at that field. If it is not present, then we can assume SIGHASH_DEFAULT or SIGHASH_ALL.
+        if (input.sighash_type != std::nullopt && (*input.sighash_type & 0x80) != SIGHASH_ANYONECANPAY) {
+            to_drop.clear();
+            break;
+        }
+
         if (input.non_witness_utxo) {
             to_drop.push_back(i);
         }
@@ -475,7 +523,6 @@ void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx, const int&
         psbtx.inputs.at(i).non_witness_utxo = nullptr;
     }
 }
-}
 
 bool FinalizePSBT(PartiallySignedTransaction& psbtx)
 {
@@ -486,7 +533,8 @@ bool FinalizePSBT(PartiallySignedTransaction& psbtx)
     bool complete = true;
     const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, SIGHASH_ALL, nullptr, true);
+        PSBTInput& input = psbtx.inputs.at(i);
+        complete &= (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, input.sighash_type, nullptr, true) == PSBTError::OK);
     }
 
     return complete;

src/psbt.h

@@ -5,6 +5,7 @@
 #ifndef BITCOIN_PSBT_H
 #define BITCOIN_PSBT_H
 
+#include <common/types.h>
 #include <node/transaction.h>
 #include <policy/feerate.h>
 #include <primitives/transaction.h>
@@ -21,6 +22,8 @@ namespace node {
 enum class TransactionError;
 } // namespace node
 
+using common::PSBTError;
+
 // Magic bytes
 static constexpr uint8_t PSBT_MAGIC_BYTES[5] = {'p', 's', 'b', 't', 0xff};
 
@@ -50,6 +53,9 @@ static constexpr uint8_t PSBT_IN_TAP_LEAF_SCRIPT = 0x15;
 static constexpr uint8_t PSBT_IN_TAP_BIP32_DERIVATION = 0x16;
 static constexpr uint8_t PSBT_IN_TAP_INTERNAL_KEY = 0x17;
 static constexpr uint8_t PSBT_IN_TAP_MERKLE_ROOT = 0x18;
+static constexpr uint8_t PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS = 0x1a;
+static constexpr uint8_t PSBT_IN_MUSIG2_PUB_NONCE = 0x1b;
+static constexpr uint8_t PSBT_IN_MUSIG2_PARTIAL_SIG = 0x1c;
 static constexpr uint8_t PSBT_IN_PROPRIETARY = 0xFC;
 
 // Output types
@@ -59,6 +65,7 @@ static constexpr uint8_t PSBT_OUT_BIP32_DERIVATION = 0x02;
 static constexpr uint8_t PSBT_OUT_TAP_INTERNAL_KEY = 0x05;
 static constexpr uint8_t PSBT_OUT_TAP_TREE = 0x06;
 static constexpr uint8_t PSBT_OUT_TAP_BIP32_DERIVATION = 0x07;
+static constexpr uint8_t PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS = 0x08;
 static constexpr uint8_t PSBT_OUT_PROPRIETARY = 0xFC;
 
 // The separator is 0x00. Reading this in means that the unserializer can interpret it
@@ -217,6 +224,11 @@ struct PSBTInput
     XOnlyPubKey m_tap_internal_key;
     uint256 m_tap_merkle_root;
 
+    // MuSig2 fields
+    std::map<CPubKey, std::vector<CPubKey>> m_musig2_participants;
+    std::map<std::pair<CPubKey, uint256>, std::map<CPubKey, std::vector<uint8_t>>> m_musig2_pubnonces;
+    std::map<std::pair<CPubKey, uint256>, std::map<CPubKey, uint256>> m_musig2_partial_sigs;
+
     std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
     std::set<PSBTProprietary> m_proprietary;
     std::optional<int> sighash_type;
@@ -337,6 +349,43 @@ struct PSBTInput
                 SerializeToVector(s, PSBT_IN_TAP_MERKLE_ROOT);
                 SerializeToVector(s, m_tap_merkle_root);
             }
+
+            // Write MuSig2 Participants
+            for (const auto& [agg_key, part_pubs] : m_musig2_participants) {
+                SerializeToVector(s, CompactSizeWriter(PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS), Span{agg_key});
+                std::vector<unsigned char> value;
+                VectorWriter s_value{value, 0};
+                for (auto& pk : part_pubs) {
+                    s_value << Span{pk};
+                }
+                s << value;
+            }
+
+            // Write MuSig2 pubnonces
+            for (const auto& [agg_key_leaf_hash, pubnonces] : m_musig2_pubnonces) {
+                const auto& [agg_key, leaf_hash] = agg_key_leaf_hash;
+                for (const auto& [pubkey, pubnonce] : pubnonces) {
+                    if (leaf_hash.IsNull()) {
+                        SerializeToVector(s, CompactSizeWriter(PSBT_IN_MUSIG2_PUB_NONCE), Span{pubkey}, Span{agg_key});
+                    } else {
+                        SerializeToVector(s, CompactSizeWriter(PSBT_IN_MUSIG2_PUB_NONCE), Span{pubkey}, Span{agg_key}, leaf_hash);
+                    }
+                    s << pubnonce;
+                }
+            }
+
+            // Write MuSig2 partial signatures
+            for (const auto& [agg_key_leaf_hash, psigs] : m_musig2_partial_sigs) {
+                const auto& [agg_key, leaf_hash] = agg_key_leaf_hash;
+                for (const auto& [pubkey, psig] : psigs) {
+                    if (leaf_hash.IsNull()) {
+                        SerializeToVector(s, CompactSizeWriter(PSBT_IN_MUSIG2_PARTIAL_SIG), Span{pubkey}, Span{agg_key});
+                    } else {
+                        SerializeToVector(s, CompactSizeWriter(PSBT_IN_MUSIG2_PARTIAL_SIG), Span{pubkey}, Span{agg_key}, leaf_hash);
+                    }
+                    SerializeToVector(s, psig);
+                }
+            }
         }
 
         // Write script sig
@@ -672,6 +721,83 @@ struct PSBTInput
                     UnserializeFromVector(s, m_tap_merkle_root);
                     break;
                 }
+                case PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS:
+                {
+                    if (!key_lookup.emplace(key).second) {
+                        throw std::ios_base::failure("Duplicate Key, input participant pubkeys for an aggregate key already provided");
+                    } else if (key.size() != 34) {
+                        throw std::ios_base::failure("Input musig2 participants pubkeys aggregate key is not 34 bytes");
+                    }
+                    std::array<unsigned char, 33> agg_key_bytes;
+                    skey >> AsWritableBytes(Span{agg_key_bytes});
+                    CPubKey agg_key(agg_key_bytes);
+
+                    std::vector<CPubKey> participants;
+                    std::vector<unsigned char> val;
+                    s >> val;
+                    SpanReader s_val{val};
+                    while (s_val.size() >= 33) {
+                        std::array<unsigned char, 33> part_key_bytes;
+                        s_val >> AsWritableBytes(Span{part_key_bytes});
+                        participants.emplace_back(Span{part_key_bytes});
+                    }
+                    if (!s_val.empty()) {
+                        throw std::ios_base::failure("Input musig2 particiapnts pubkeys value size is not a multiple of 33");
+                    }
+
+                    m_musig2_participants.emplace(agg_key, participants);
+                    break;
+                }
+                case PSBT_IN_MUSIG2_PUB_NONCE:
+                {
+                    if (!key_lookup.emplace(key).second) {
+                        throw std::ios_base::failure("Duplicate Key, input musig2 pubnonce already provided");
+                    } else if (key.size() != 67 && key.size() != 99) {
+                        throw std::ios_base::failure("Input musig2 pubnonce key is not expected size");
+                    }
+                    std::array<unsigned char, 33> part_pubkey_bytes;
+                    std::array<unsigned char, 33> agg_pubkey_bytes;
+                    uint256 leaf_hash;
+
+                    skey >> AsWritableBytes(Span{part_pubkey_bytes}) >> AsWritableBytes(Span{agg_pubkey_bytes});
+                    CPubKey agg_pub{Span{agg_pubkey_bytes}};
+                    CPubKey part_pub{Span{part_pubkey_bytes}};
+
+                    if (!skey.empty()) {
+                        skey >> leaf_hash;
+                    }
+
+                    std::vector<uint8_t> pubnonce;
+                    s >> pubnonce;
+
+                    m_musig2_pubnonces[std::make_pair(agg_pub, leaf_hash)].emplace(part_pub, pubnonce);
+                    break;
+                }
+                case PSBT_IN_MUSIG2_PARTIAL_SIG:
+                {
+                    if (!key_lookup.emplace(key).second) {
+                        throw std::ios_base::failure("Duplicate Key, input musig2 partial sig already provided");
+                    } else if (key.size() != 67 && key.size() != 99) {
+                        throw std::ios_base::failure("Input musig2 partial sig key is not expected size");
+                    }
+                    std::array<unsigned char, 33> part_pubkey_bytes;
+                    std::array<unsigned char, 33> agg_pubkey_bytes;
+                    uint256 leaf_hash;
+
+                    skey >> AsWritableBytes(Span{part_pubkey_bytes}) >> AsWritableBytes(Span{agg_pubkey_bytes});
+                    CPubKey agg_pub{Span{agg_pubkey_bytes}};
+                    CPubKey part_pub{Span{part_pubkey_bytes}};
+
+                    if (!skey.empty()) {
+                        skey >> leaf_hash;
+                    }
+
+                    uint256 partial_sig;
+                    UnserializeFromVector(s, partial_sig);
+
+                    m_musig2_partial_sigs[std::make_pair(agg_pub, leaf_hash)].emplace(part_pub, partial_sig);
+                    break;
+                }
                 case PSBT_IN_PROPRIETARY:
                 {
                     PSBTProprietary this_prop;
@@ -719,6 +845,7 @@ struct PSBTOutput
     XOnlyPubKey m_tap_internal_key;
     std::vector<std::tuple<uint8_t, uint8_t, std::vector<unsigned char>>> m_tap_tree;
     std::map<XOnlyPubKey, std::pair<std::set<uint256>, KeyOriginInfo>> m_tap_bip32_paths;
+    std::map<CPubKey, std::vector<CPubKey>> m_musig2_participants;
     std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
     std::set<PSBTProprietary> m_proprietary;
 
@@ -781,6 +908,17 @@ struct PSBTOutput
             s << value;
         }
 
+        // Write MuSig2 Participants
+        for (const auto& [agg_key, part_pubs] : m_musig2_participants) {
+            SerializeToVector(s, CompactSizeWriter(PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS), Span{agg_key});
+            std::vector<unsigned char> value;
+            VectorWriter s_value{value, 0};
+            for (auto& pk : part_pubs) {
+                s_value << Span{pk};
+            }
+            s << value;
+        }
+
         // Write unknown things
         for (auto& entry : unknown) {
             s << entry.first;
@@ -907,6 +1045,33 @@ struct PSBTOutput
                     m_tap_bip32_paths.emplace(xonly, std::make_pair(leaf_hashes, DeserializeKeyOrigin(s, origin_len)));
                     break;
                 }
+                case PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS:
+                {
+                    if (!key_lookup.emplace(key).second) {
+                        throw std::ios_base::failure("Duplicate Key, output participant pubkeys for an aggregate key already provided");
+                    } else if (key.size() != 34) {
+                        throw std::ios_base::failure("Output musig2 participants pubkeys aggregate key is not 34 bytes");
+                    }
+                    std::array<unsigned char, 33> agg_key_bytes;
+                    skey.read(AsWritableBytes(Span{agg_key_bytes}));
+                    CPubKey agg_key(agg_key_bytes);
+
+                    std::vector<CPubKey> participants;
+                    std::vector<unsigned char> val;
+                    s >> val;
+                    SpanReader s_val{val};
+                    while (s_val.size() >= 33) {
+                        std::array<unsigned char, 33> part_key_bytes;
+                        s_val.read(AsWritableBytes(Span{part_key_bytes}));
+                        participants.emplace_back(Span{part_key_bytes});
+                    }
+                    if (!s_val.empty()) {
+                        throw std::ios_base::failure("Input musig2 particiapnts pubkeys value size is not a multiple of 33");
+                    }
+
+                    m_musig2_participants.emplace(agg_key, participants);
+                    break;
+                }
                 case PSBT_OUT_PROPRIETARY:
                 {
                     PSBTProprietary this_prop;
@@ -1236,10 +1401,10 @@ bool PSBTInputSignedAndVerified(const PartiallySignedTransaction psbt, unsigned
  * txdata should be the output of PrecomputePSBTData (which can be shared across
  * multiple SignPSBTInput calls). If it is nullptr, a dummy signature will be created.
  **/
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash = SIGHASH_ALL, SignatureData* out_sigdata = nullptr, bool finalize = true);
+[[nodiscard]] PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, std::optional<int> sighash = std::nullopt, SignatureData* out_sigdata = nullptr, bool finalize = true);
 
 /**  Reduces the size of the PSBT by dropping unnecessary `non_witness_utxos` (i.e. complete previous transactions) from a psbt when all inputs are segwit v1. */
-void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx, const int& sighash_type);
+void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx);
 
 /** Counts the unsigned inputs of a PSBT. */
 size_t CountPSBTUnsignedInputs(const PartiallySignedTransaction& psbt);

src/pubkey.cpp

@@ -197,20 +197,29 @@ constexpr XOnlyPubKey XOnlyPubKey::NUMS_H{
     []() consteval { return XOnlyPubKey{"50929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0"_hex_u8}; }(),
 };
 
+std::vector<CPubKey> XOnlyPubKey::GetCPubKeys() const
+{
+    std::vector<CPubKey> out;
+    unsigned char b[33] = {0x02};
+    std::copy(m_keydata.begin(), m_keydata.end(), b + 1);
+    CPubKey fullpubkey;
+    fullpubkey.Set(b, b + 33);
+    out.push_back(fullpubkey);
+    b[0] = 0x03;
+    fullpubkey.Set(b, b + 33);
+    out.push_back(fullpubkey);
+    return out;
+}
+
 std::vector<CKeyID> XOnlyPubKey::GetKeyIDs() const
 {
     std::vector<CKeyID> out;
     // For now, use the old full pubkey-based key derivation logic. As it is indexed by
     // Hash160(full pubkey), we need to return both a version prefixed with 0x02, and one
     // with 0x03.
-    unsigned char b[33] = {0x02};
+    for (const CPubKey& pk : GetCPubKeys()) {
-    std::copy(m_keydata.begin(), m_keydata.end(), b + 1);
+        out.push_back(pk.GetID());
-    CPubKey fullpubkey;
+    }
-    fullpubkey.Set(b, b + 33);
-    out.push_back(fullpubkey.GetID());
-    b[0] = 0x03;
-    fullpubkey.Set(b, b + 33);
-    out.push_back(fullpubkey.GetID());
     return out;
 }
 
@@ -332,13 +341,14 @@ bool CPubKey::Decompress() {
     return true;
 }
 
-bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
+bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc, uint256& tweak_out) const {
     assert(IsValid());
     assert((nChild >> 31) == 0);
     assert(size() == COMPRESSED_SIZE);
     unsigned char out[64];
     BIP32Hash(cc, nChild, *begin(), begin()+1, out);
     memcpy(ccChild.begin(), out+32, 32);
+    memcpy(tweak_out.begin(), out, 32);
     secp256k1_pubkey pubkey;
     if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, vch, size())) {
         return false;
@@ -404,12 +414,17 @@ void CExtPubKey::DecodeWithVersion(const unsigned char code[BIP32_EXTKEY_WITH_VE
 }
 
 bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
+    uint256 tweak;
+    return Derive(out, _nChild, tweak);
+}
+
+bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild, uint256& tweak_out) const {
     if (nDepth == std::numeric_limits<unsigned char>::max()) return false;
     out.nDepth = nDepth + 1;
     CKeyID id = pubkey.GetID();
     memcpy(out.vchFingerprint, &id, 4);
     out.nChild = _nChild;
-    return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
+    return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode, tweak_out);
 }
 
 /* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {

src/pubkey.h

@@ -224,7 +224,7 @@ public:
     bool Decompress();
 
     //! Derive BIP32 child pubkey.
-    [[nodiscard]] bool Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const;
+    [[nodiscard]] bool Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc, uint256& tweak_out) const;
 };
 
 class XOnlyPubKey
@@ -286,6 +286,7 @@ public:
      * This is needed for key lookups since keys are indexed by CKeyID.
      */
     std::vector<CKeyID> GetKeyIDs() const;
+    std::vector<CPubKey> GetCPubKeys() const;
 
     CPubKey GetEvenCorrespondingCPubKey() const;
 
@@ -376,6 +377,7 @@ struct CExtPubKey {
     void EncodeWithVersion(unsigned char code[BIP32_EXTKEY_WITH_VERSION_SIZE]) const;
     void DecodeWithVersion(const unsigned char code[BIP32_EXTKEY_WITH_VERSION_SIZE]);
     [[nodiscard]] bool Derive(CExtPubKey& out, unsigned int nChild) const;
+    [[nodiscard]] bool Derive(CExtPubKey& out, unsigned int nChild, uint256& tweak_out) const;
 };
 
 #endif // BITCOIN_PUBKEY_H

src/qt/psbtoperationsdialog.cpp

@@ -59,7 +59,7 @@ void PSBTOperationsDialog::openWithPSBT(PartiallySignedTransaction psbtx)
     bool complete = FinalizePSBT(psbtx); // Make sure all existing signatures are fully combined before checking for completeness.
     if (m_wallet_model) {
         size_t n_could_sign;
-        const auto err{m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, &n_could_sign, m_transaction_data, complete)};
+        const auto err{m_wallet_model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, &n_could_sign, m_transaction_data, complete)};
         if (err) {
             showStatus(tr("Failed to load transaction: %1")
                            .arg(QString::fromStdString(PSBTErrorString(*err).translated)),
@@ -83,7 +83,7 @@ void PSBTOperationsDialog::signTransaction()
 
     WalletModel::UnlockContext ctx(m_wallet_model->requestUnlock());
 
-    const auto err{m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/true, /*bip32derivs=*/true, &n_signed, m_transaction_data, complete)};
+    const auto err{m_wallet_model->wallet().fillPSBT(std::nullopt, /*sign=*/true, /*bip32derivs=*/true, &n_signed, m_transaction_data, complete)};
 
     if (err) {
         showStatus(tr("Failed to sign transaction: %1")
@@ -251,7 +251,7 @@ size_t PSBTOperationsDialog::couldSignInputs(const PartiallySignedTransaction &p
 
     size_t n_signed;
     bool complete;
-    const auto err{m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/false, &n_signed, m_transaction_data, complete)};
+    const auto err{m_wallet_model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/false, &n_signed, m_transaction_data, complete)};
 
     if (err) {
         return 0;

src/qt/sendcoinsdialog.cpp

@@ -446,7 +446,7 @@ void SendCoinsDialog::presentPSBT(PartiallySignedTransaction& psbtx)
 bool SendCoinsDialog::signWithExternalSigner(PartiallySignedTransaction& psbtx, CMutableTransaction& mtx, bool& complete) {
     std::optional<PSBTError> err;
     try {
-        err = model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/true, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete);
+        err = model->wallet().fillPSBT(std::nullopt, /*sign=*/true, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete);
     } catch (const std::runtime_error& e) {
         QMessageBox::critical(nullptr, tr("Sign failed"), e.what());
         return false;
@@ -503,7 +503,7 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
         // Fill without signing
-        const auto err{model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
+        const auto err{model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
         assert(!complete);
         assert(!err);
 
@@ -519,7 +519,7 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
             bool complete = false;
             // Always fill without signing first. This prevents an external signer
             // from being called prematurely and is not expensive.
-            const auto err{model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
+            const auto err{model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
             assert(!complete);
             assert(!err);
             send_failure = !signWithExternalSigner(psbtx, mtx, complete);

src/qt/walletmodel.cpp

@@ -535,7 +535,7 @@ bool WalletModel::bumpFee(uint256 hash, uint256& new_hash)
         // "Create Unsigned" clicked
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const auto err{wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, nullptr, psbtx, complete)};
+        const auto err{wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, nullptr, psbtx, complete)};
         if (err || complete) {
             QMessageBox::critical(nullptr, tr("Fee bump error"), tr("Can't draft transaction."));
             return false;

src/rpc/rawtransaction.cpp

@@ -163,7 +163,7 @@ static std::vector<RPCArg> CreateTxDoc()
 
 // Update PSBT with information from the mempool, the UTXO set, the txindex, and the provided descriptors.
 // Optionally, sign the inputs that we can using information from the descriptors.
-PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std::any& context, const HidingSigningProvider& provider, int sighash_type, bool finalize)
+PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std::any& context, const HidingSigningProvider& provider, std::optional<int> sighash_type, bool finalize)
 {
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
@@ -235,7 +235,10 @@ PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std
         // Note that SignPSBTInput does a lot more than just constructing ECDSA signatures.
         // We only actually care about those if our signing provider doesn't hide private
         // information, as is the case with `descriptorprocesspsbt`
-        SignPSBTInput(provider, psbtx, /*index=*/i, &txdata, sighash_type, /*out_sigdata=*/nullptr, finalize);
+        // Only error for mismatching sighash types as it is critical that the sighash to sign with matches the PSBT's
+        if (SignPSBTInput(provider, psbtx, /*index=*/i, &txdata, sighash_type, /*out_sigdata=*/nullptr, finalize) == common::PSBTError::SIGHASH_MISMATCH) {
+            throw JSONRPCPSBTError(common::PSBTError::SIGHASH_MISMATCH);
+        }
     }
 
     // Update script/keypath information using descriptor data.
@@ -243,7 +246,7 @@ PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std
         UpdatePSBTOutput(provider, psbtx, i);
     }
 
-    RemoveUnnecessaryTransactions(psbtx, /*sighash_type=*/1);
+    RemoveUnnecessaryTransactions(psbtx);
 
     return psbtx;
 }
@@ -916,6 +919,37 @@ const RPCResult decodepsbt_inputs{
             }},
             {RPCResult::Type::STR_HEX, "taproot_internal_key", /*optional=*/ true, "The hex-encoded Taproot x-only internal key"},
             {RPCResult::Type::STR_HEX, "taproot_merkle_root", /*optional=*/ true, "The hex-encoded Taproot merkle root"},
+            {RPCResult::Type::ARR, "musig2_participant_pubkeys", /*optional=*/true, "",
+            {
+                {RPCResult::Type::OBJ, "", "",
+                {
+                    {RPCResult::Type::STR_HEX, "aggregate_pubkey", "The plain aggregate public key for which the participants create."},
+                    {RPCResult::Type::ARR, "participant_pubkeys", "",
+                    {
+                        {RPCResult::Type::STR_HEX, "pubkey", "The plain public keys that are aggregated for aggregate_pubkey."},
+                    }},
+                }},
+            }},
+            {RPCResult::Type::ARR, "musig2_pubnonces", /*optional=*/true, "",
+            {
+                {RPCResult::Type::OBJ, "", "",
+                {
+                    {RPCResult::Type::STR_HEX, "participant_pubkey", "The plain public key of the participant that created this pubnonce."},
+                    {RPCResult::Type::STR_HEX, "aggregate_pubkey", "The plain aggregate public key for which this pubnonce is for."},
+                    {RPCResult::Type::STR_HEX, "leaf_hash", /*optional=*/true, "The hash of the leaf script that contains the aggregate pubkey being signed for. Omitted when signing for the internal key."},
+                    {RPCResult::Type::STR_HEX, "pubnonce", "The public nonce itself."},
+                }},
+            }},
+            {RPCResult::Type::ARR, "musig2_partial_sigs", /*optional=*/true, "",
+            {
+                {RPCResult::Type::OBJ, "", "",
+                {
+                    {RPCResult::Type::STR_HEX, "participant_pubkey", "The plain public key of the participant that created this partial signature."},
+                    {RPCResult::Type::STR_HEX, "aggregate_pubkey", "The plain aggregate public key for which this partial signature is for."},
+                    {RPCResult::Type::STR_HEX, "leaf_hash", /*optional=*/true, "The hash of the leaf script that contains the aggregate pubkey being signed for. Omitted when signing for the internal key."},
+                    {RPCResult::Type::STR_HEX, "partial_sig", "The partial signature itself."},
+                }},
+            }},
             {RPCResult::Type::OBJ_DYN, "unknown", /*optional=*/ true, "The unknown input fields",
             {
                 {RPCResult::Type::STR_HEX, "key", "(key-value pair) An unknown key-value pair"},
@@ -983,6 +1017,17 @@ const RPCResult decodepsbt_outputs{
                     }},
                 }},
             }},
+            {RPCResult::Type::ARR, "musig2_participant_pubkeys", /*optional=*/true, "",
+            {
+                {RPCResult::Type::OBJ, "", "",
+                {
+                    {RPCResult::Type::STR_HEX, "aggregate_pubkey", "The plain aggregate public key for which the participants create."},
+                    {RPCResult::Type::ARR, "participant_pubkeys", "",
+                    {
+                        {RPCResult::Type::STR_HEX, "pubkey", "The plain public keys that are aggregated for aggregate_pubkey."},
+                    }},
+                }},
+            }},
             {RPCResult::Type::OBJ_DYN, "unknown", /*optional=*/true, "The unknown output fields",
             {
                 {RPCResult::Type::STR_HEX, "key", "(key-value pair) An unknown key-value pair"},
@@ -1304,6 +1349,52 @@ static RPCHelpMan decodepsbt()
             in.pushKV("taproot_merkle_root", HexStr(input.m_tap_merkle_root));
         }
 
+        // Write MuSig2 fields
+        if (!input.m_musig2_participants.empty()) {
+            UniValue musig_keys(UniValue::VARR);
+            for (const auto& [agg, parts] : input.m_musig2_participants) {
+                UniValue musig_part(UniValue::VOBJ);
+                musig_part.pushKV("aggregate_pubkey", HexStr(agg));
+                UniValue part_keys(UniValue::VARR);
+                for (const auto& pub : parts) {
+                    part_keys.push_back(HexStr(pub));
+                }
+                musig_part.pushKV("participant_pubkeys", part_keys);
+                musig_keys.push_back(musig_part);
+            }
+            in.pushKV("musig2_participant_pubkeys", musig_keys);
+        }
+        if (!input.m_musig2_pubnonces.empty()) {
+            UniValue musig_pubnonces(UniValue::VARR);
+            for (const auto& [agg_lh, part_pubnonce] : input.m_musig2_pubnonces) {
+                const auto& [agg, lh] = agg_lh;
+                for (const auto& [part, pubnonce] : part_pubnonce) {
+                    UniValue info(UniValue::VOBJ);
+                    info.pushKV("participant_pubkey", HexStr(part));
+                    info.pushKV("aggregate_pubkey", HexStr(agg));
+                    if (!lh.IsNull()) info.pushKV("leaf_hash", HexStr(lh));
+                    info.pushKV("pubnonce", HexStr(pubnonce));
+                    musig_pubnonces.push_back(info);
+                }
+            }
+            in.pushKV("musig2_pubnonces", musig_pubnonces);
+        }
+        if (!input.m_musig2_partial_sigs.empty()) {
+            UniValue musig_partial_sigs(UniValue::VARR);
+            for (const auto& [agg_lh, part_psig] : input.m_musig2_partial_sigs) {
+                const auto& [agg, lh] = agg_lh;
+                for (const auto& [part, psig] : part_psig) {
+                    UniValue info(UniValue::VOBJ);
+                    info.pushKV("participant_pubkey", HexStr(part));
+                    info.pushKV("aggregate_pubkey", HexStr(agg));
+                    if (!lh.IsNull()) info.pushKV("leaf_hash", HexStr(lh));
+                    info.pushKV("partial_sig", HexStr(psig));
+                    musig_partial_sigs.push_back(info);
+                }
+            }
+            in.pushKV("musig2_partial_sigs", musig_partial_sigs);
+        }
+
         // Proprietary
         if (!input.m_proprietary.empty()) {
             UniValue proprietary(UniValue::VARR);
@@ -1399,6 +1490,22 @@ static RPCHelpMan decodepsbt()
             out.pushKV("taproot_bip32_derivs", std::move(keypaths));
         }
 
+        // Write MuSig2 fields
+        if (!output.m_musig2_participants.empty()) {
+            UniValue musig_keys(UniValue::VARR);
+            for (const auto& [agg, parts] : output.m_musig2_participants) {
+                UniValue musig_part(UniValue::VOBJ);
+                musig_part.pushKV("aggregate_pubkey", HexStr(agg));
+                UniValue part_keys(UniValue::VARR);
+                for (const auto& pub : parts) {
+                    part_keys.push_back(HexStr(pub));
+                }
+                musig_part.pushKV("participant_pubkeys", part_keys);
+                musig_keys.push_back(musig_part);
+            }
+            out.pushKV("musig2_participant_pubkeys", musig_keys);
+        }
+
         // Proprietary
         if (!output.m_proprietary.empty()) {
             UniValue proprietary(UniValue::VARR);
@@ -1689,7 +1796,7 @@ static RPCHelpMan utxoupdatepsbt()
         request.params[0].get_str(),
         request.context,
         HidingSigningProvider(&provider, /*hide_secret=*/true, /*hide_origin=*/false),
-        /*sighash_type=*/SIGHASH_ALL,
+        /*sighash_type=*/std::nullopt,
         /*finalize=*/false);
 
     DataStream ssTx{};
@@ -1956,7 +2063,7 @@ RPCHelpMan descriptorprocesspsbt()
         EvalDescriptorStringOrObject(descs[i], provider, /*expand_priv=*/true);
     }
 
-    int sighash_type = ParseSighashString(request.params[2]);
+    std::optional<int> sighash_type = ParseSighashString(request.params[2]);
     bool bip32derivs = request.params[3].isNull() ? true : request.params[3].get_bool();
     bool finalize = request.params[4].isNull() ? true : request.params[4].get_bool();
 

src/rpc/rawtransaction_util.cpp

@@ -304,12 +304,15 @@ void ParsePrevouts(const UniValue& prevTxsUnival, FlatSigningProvider* keystore,
 
 void SignTransaction(CMutableTransaction& mtx, const SigningProvider* keystore, const std::map<COutPoint, Coin>& coins, const UniValue& hashType, UniValue& result)
 {
-    int nHashType = ParseSighashString(hashType);
+    std::optional<int> nHashType = ParseSighashString(hashType);
+    if (!nHashType) {
+        nHashType = SIGHASH_DEFAULT;
+    }
 
     // Script verification errors
     std::map<int, bilingual_str> input_errors;
 
-    bool complete = SignTransaction(mtx, keystore, coins, nHashType, input_errors);
+    bool complete = SignTransaction(mtx, keystore, coins, *nHashType, input_errors);
     SignTransactionResultToJSON(mtx, complete, coins, input_errors, result);
 }
 

src/rpc/util.cpp

@@ -378,10 +378,10 @@ UniValue DescribeAddress(const CTxDestination& dest)
  *
  * @pre The sighash argument should be string or null.
 */
-int ParseSighashString(const UniValue& sighash)
+std::optional<int> ParseSighashString(const UniValue& sighash)
 {
     if (sighash.isNull()) {
-        return SIGHASH_DEFAULT;
+        return std::nullopt;
     }
     const auto result{SighashFromStr(sighash.get_str())};
     if (!result) {

src/rpc/util.h

@@ -138,7 +138,7 @@ CTxDestination AddAndGetMultisigDestination(const int required, const std::vecto
 UniValue DescribeAddress(const CTxDestination& dest);
 
 /** Parse a sighash string representation and raise an RPC error if it is invalid. */
-int ParseSighashString(const UniValue& sighash);
+std::optional<int> ParseSighashString(const UniValue& sighash);
 
 //! Parse a confirm target option and raise an RPC error if it is invalid.
 unsigned int ParseConfirmTarget(const UniValue& value, unsigned int max_target);

src/script/descriptor.cpp

@@ -7,6 +7,7 @@
 #include <hash.h>
 #include <key_io.h>
 #include <pubkey.h>
+#include <musig.h>
 #include <script/miniscript.h>
 #include <script/parsing.h>
 #include <script/script.h>
@@ -174,12 +175,10 @@ public:
      * Used by the Miniscript descriptors to check for duplicate keys in the script.
      */
     bool operator<(PubkeyProvider& other) const {
-        CPubKey a, b;
+        FlatSigningProvider dummy;
-        SigningProvider dummy;
-        KeyOriginInfo dummy_info;
 
-        GetPubKey(0, dummy, a, dummy_info);
+        std::optional<CPubKey> a = GetPubKey(0, dummy, dummy);
-        other.GetPubKey(0, dummy, b, dummy_info);
+        std::optional<CPubKey> b = other.GetPubKey(0, dummy, dummy);
 
         return a < b;
     }
@@ -189,7 +188,7 @@ public:
      *  write_cache is the cache to write keys to (if not nullptr)
      *  Caches are not exclusive but this is not tested. Currently we use them exclusively
      */
-    virtual bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const = 0;
+    virtual std::optional<CPubKey> GetPubKey(int pos, const SigningProvider& arg, FlatSigningProvider& out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const = 0;
 
     /** Whether this represent multiple public keys at different positions. */
     virtual bool IsRange() const = 0;
@@ -213,8 +212,8 @@ public:
      */
     virtual bool ToNormalizedString(const SigningProvider& arg, std::string& out, const DescriptorCache* cache = nullptr) const = 0;
 
-    /** Derive a private key, if private data is available in arg. */
+    /** Derive a private key, if private data is available in arg and put it into out. */
-    virtual bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const = 0;
+    virtual void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const = 0;
 
     /** Return the non-extended public key for this PubkeyProvider, if it has one. */
     virtual std::optional<CPubKey> GetRootPubKey() const = 0;
@@ -223,6 +222,9 @@ public:
 
     /** Make a deep copy of this PubkeyProvider */
     virtual std::unique_ptr<PubkeyProvider> Clone() const = 0;
+
+    /** Whether this PubkeyProvider can be a BIP 32 extended key that can be derived from */
+    virtual bool IsBIP32() const = 0;
 };
 
 class OriginPubkeyProvider final : public PubkeyProvider
@@ -240,15 +242,20 @@ class OriginPubkeyProvider final : public PubkeyProvider
 
 public:
     OriginPubkeyProvider(uint32_t exp_index, KeyOriginInfo info, std::unique_ptr<PubkeyProvider> provider, bool apostrophe) : PubkeyProvider(exp_index), m_origin(std::move(info)), m_provider(std::move(provider)), m_apostrophe(apostrophe) {}
-    bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
+    std::optional<CPubKey> GetPubKey(int pos, const SigningProvider& arg, FlatSigningProvider& out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
     {
-        if (!m_provider->GetPubKey(pos, arg, key, info, read_cache, write_cache)) return false;
+        std::optional<CPubKey> pub = m_provider->GetPubKey(pos, arg, out, read_cache, write_cache);
-        std::copy(std::begin(m_origin.fingerprint), std::end(m_origin.fingerprint), info.fingerprint);
+        if (!pub) return std::nullopt;
-        info.path.insert(info.path.begin(), m_origin.path.begin(), m_origin.path.end());
+        Assert(out.pubkeys.contains(pub->GetID()));
-        return true;
+        auto& [pubkey, suborigin] = out.origins[pub->GetID()];
+        Assert(pubkey == *pub); // All subproviders must be inserting a valid origin already
+        std::copy(std::begin(m_origin.fingerprint), std::end(m_origin.fingerprint), suborigin.fingerprint);
+        suborigin.path.insert(suborigin.path.begin(), m_origin.path.begin(), m_origin.path.end());
+        return pub;
     }
     bool IsRange() const override { return m_provider->IsRange(); }
     size_t GetSize() const override { return m_provider->GetSize(); }
+    bool IsBIP32() const override { return m_provider->IsBIP32(); }
     std::string ToString(StringType type) const override { return "[" + OriginString(type) + "]" + m_provider->ToString(type); }
     bool ToPrivateString(const SigningProvider& arg, std::string& ret) const override
     {
@@ -272,9 +279,9 @@ public:
         }
         return true;
     }
-    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
     {
-        return m_provider->GetPrivKey(pos, arg, key);
+        m_provider->GetPrivKey(pos, arg, out);
     }
     std::optional<CPubKey> GetRootPubKey() const override
     {
@@ -296,24 +303,34 @@ class ConstPubkeyProvider final : public PubkeyProvider
     CPubKey m_pubkey;
     bool m_xonly;
 
+    std::optional<CKey> GetPrivKey(const SigningProvider& arg) const
+    {
+        CKey key;
+        if (!(m_xonly ? arg.GetKeyByXOnly(XOnlyPubKey(m_pubkey), key) :
+                        arg.GetKey(m_pubkey.GetID(), key))) return std::nullopt;
+        return key;
+    }
+
 public:
     ConstPubkeyProvider(uint32_t exp_index, const CPubKey& pubkey, bool xonly) : PubkeyProvider(exp_index), m_pubkey(pubkey), m_xonly(xonly) {}
-    bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
+    std::optional<CPubKey> GetPubKey(int pos, const SigningProvider& arg, FlatSigningProvider& out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
     {
-        key = m_pubkey;
+        KeyOriginInfo info;
-        info.path.clear();
         CKeyID keyid = m_pubkey.GetID();
         std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
-        return true;
+        out.origins.emplace(keyid, std::make_pair(m_pubkey, info));
+        out.pubkeys.emplace(keyid, m_pubkey);
+        return m_pubkey;
     }
     bool IsRange() const override { return false; }
     size_t GetSize() const override { return m_pubkey.size(); }
+    bool IsBIP32() const override { return false; }
     std::string ToString(StringType type) const override { return m_xonly ? HexStr(m_pubkey).substr(2) : HexStr(m_pubkey); }
     bool ToPrivateString(const SigningProvider& arg, std::string& ret) const override
     {
-        CKey key;
+        std::optional<CKey> key = GetPrivKey(arg);
-        if (!GetPrivKey(/*pos=*/0, arg, key)) return false;
+        if (!key) return false;
-        ret = EncodeSecret(key);
+        ret = EncodeSecret(*key);
         return true;
     }
     bool ToNormalizedString(const SigningProvider& arg, std::string& ret, const DescriptorCache* cache) const override
@@ -321,10 +338,11 @@ public:
         ret = ToString(StringType::PUBLIC);
         return true;
     }
-    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
     {
-        return m_xonly ? arg.GetKeyByXOnly(XOnlyPubKey(m_pubkey), key) :
+        std::optional<CKey> key = GetPrivKey(arg);
-                         arg.GetKey(m_pubkey.GetID(), key);
+        if (!key) return;
+        out.keys.emplace(key->GetPubKey().GetID(), *key);
     }
     std::optional<CPubKey> GetRootPubKey() const override
     {
@@ -394,18 +412,18 @@ public:
     BIP32PubkeyProvider(uint32_t exp_index, const CExtPubKey& extkey, KeyPath path, DeriveType derive, bool apostrophe) : PubkeyProvider(exp_index), m_root_extkey(extkey), m_path(std::move(path)), m_derive(derive), m_apostrophe(apostrophe) {}
     bool IsRange() const override { return m_derive != DeriveType::NO; }
     size_t GetSize() const override { return 33; }
-    bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key_out, KeyOriginInfo& final_info_out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
+    bool IsBIP32() const override { return true; }
+    std::optional<CPubKey> GetPubKey(int pos, const SigningProvider& arg, FlatSigningProvider& out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
     {
         // Info of parent of the to be derived pubkey
-        KeyOriginInfo parent_info;
+        KeyOriginInfo info;
         CKeyID keyid = m_root_extkey.pubkey.GetID();
-        std::copy(keyid.begin(), keyid.begin() + sizeof(parent_info.fingerprint), parent_info.fingerprint);
+        std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
-        parent_info.path = m_path;
+        info.path = m_path;
 
         // Info of the derived key itself which is copied out upon successful completion
-        KeyOriginInfo final_info_out_tmp = parent_info;
+        if (m_derive == DeriveType::UNHARDENED) info.path.push_back((uint32_t)pos);
-        if (m_derive == DeriveType::UNHARDENED) final_info_out_tmp.path.push_back((uint32_t)pos);
+        if (m_derive == DeriveType::HARDENED) info.path.push_back(((uint32_t)pos) | 0x80000000L);
-        if (m_derive == DeriveType::HARDENED) final_info_out_tmp.path.push_back(((uint32_t)pos) | 0x80000000L);
 
         // Derive keys or fetch them from cache
         CExtPubKey final_extkey = m_root_extkey;
@@ -414,16 +432,16 @@ public:
         bool der = true;
         if (read_cache) {
             if (!read_cache->GetCachedDerivedExtPubKey(m_expr_index, pos, final_extkey)) {
-                if (m_derive == DeriveType::HARDENED) return false;
+                if (m_derive == DeriveType::HARDENED) return std::nullopt;
                 // Try to get the derivation parent
-                if (!read_cache->GetCachedParentExtPubKey(m_expr_index, parent_extkey)) return false;
+                if (!read_cache->GetCachedParentExtPubKey(m_expr_index, parent_extkey)) return std::nullopt;
                 final_extkey = parent_extkey;
                 if (m_derive == DeriveType::UNHARDENED) der = parent_extkey.Derive(final_extkey, pos);
             }
         } else if (IsHardened()) {
             CExtKey xprv;
             CExtKey lh_xprv;
-            if (!GetDerivedExtKey(arg, xprv, lh_xprv)) return false;
+            if (!GetDerivedExtKey(arg, xprv, lh_xprv)) return std::nullopt;
             parent_extkey = xprv.Neuter();
             if (m_derive == DeriveType::UNHARDENED) der = xprv.Derive(xprv, pos);
             if (m_derive == DeriveType::HARDENED) der = xprv.Derive(xprv, pos | 0x80000000UL);
@@ -433,16 +451,16 @@ public:
             }
         } else {
             for (auto entry : m_path) {
-                if (!parent_extkey.Derive(parent_extkey, entry)) return false;
+                if (!parent_extkey.Derive(parent_extkey, entry)) return std::nullopt;
             }
             final_extkey = parent_extkey;
             if (m_derive == DeriveType::UNHARDENED) der = parent_extkey.Derive(final_extkey, pos);
             assert(m_derive != DeriveType::HARDENED);
         }
-        if (!der) return false;
+        if (!der) return std::nullopt;
 
-        final_info_out = final_info_out_tmp;
+        out.origins.emplace(final_extkey.pubkey.GetID(), std::make_pair(final_extkey.pubkey, info));
-        key_out = final_extkey.pubkey;
+        out.pubkeys.emplace(final_extkey.pubkey.GetID(), final_extkey.pubkey);
 
         if (write_cache) {
             // Only cache parent if there is any unhardened derivation
@@ -452,12 +470,12 @@ public:
                 if (last_hardened_extkey.pubkey.IsValid()) {
                     write_cache->CacheLastHardenedExtPubKey(m_expr_index, last_hardened_extkey);
                 }
-            } else if (final_info_out.path.size() > 0) {
+            } else if (info.path.size() > 0) {
                 write_cache->CacheDerivedExtPubKey(m_expr_index, pos, final_extkey);
             }
         }
 
-        return true;
+        return final_extkey.pubkey;
     }
     std::string ToString(StringType type, bool normalized) const
     {
@@ -543,15 +561,14 @@ public:
         }
         return true;
     }
-    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
     {
         CExtKey extkey;
         CExtKey dummy;
-        if (!GetDerivedExtKey(arg, extkey, dummy)) return false;
+        if (!GetDerivedExtKey(arg, extkey, dummy)) return;
-        if (m_derive == DeriveType::UNHARDENED && !extkey.Derive(extkey, pos)) return false;
+        if (m_derive == DeriveType::UNHARDENED && !extkey.Derive(extkey, pos)) return;
-        if (m_derive == DeriveType::HARDENED && !extkey.Derive(extkey, pos | 0x80000000UL)) return false;
+        if (m_derive == DeriveType::HARDENED && !extkey.Derive(extkey, pos | 0x80000000UL)) return;
-        key = extkey.key;
+        out.keys.emplace(extkey.key.GetPubKey().GetID(), extkey.key);
-        return true;
     }
     std::optional<CPubKey> GetRootPubKey() const override
     {
@@ -567,6 +584,219 @@ public:
     }
 };
 
+/** PubkeyProvider for a musig() expression */
+class MuSigPubkeyProvider final : public PubkeyProvider
+{
+private:
+    //! PubkeyProvider for the participants
+    const std::vector<std::unique_ptr<PubkeyProvider>> m_participants;
+    //! Derivation path if this is ranged
+    const KeyPath m_path;
+    //! PubkeyProvider for the aggregate pubkey if it can be cached (i.e. participants are not ranged)
+    mutable std::unique_ptr<PubkeyProvider> m_aggregate_provider;
+    mutable std::optional<CPubKey> m_aggregate_pubkey;
+    const DeriveType m_derive;
+
+    bool IsRangedDerivation() const { return m_derive != DeriveType::NO; }
+    bool IsRangedParticipants() const
+    {
+        for (const auto& pubkey : m_participants) {
+            if (pubkey->IsRange()) return true;
+        }
+        return false;
+    }
+
+public:
+    MuSigPubkeyProvider(
+        uint32_t exp_index,
+        std::vector<std::unique_ptr<PubkeyProvider>> providers,
+        KeyPath path,
+        DeriveType derive
+    )
+        : PubkeyProvider(exp_index),
+        m_participants(std::move(providers)),
+        m_path(std::move(path)),
+        m_derive(derive)
+    {}
+
+    std::optional<CPubKey> GetPubKey(int pos, const SigningProvider& arg, FlatSigningProvider& out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
+    {
+        // If the participants are not ranged, we can compute and cache the aggregate pubkey by creating a PubkeyProvider for it
+        if (!m_aggregate_provider && !IsRangedParticipants()) {
+            // Retrieve the pubkeys from the providers
+            std::vector<CPubKey> pubkeys;
+            for (const auto& prov : m_participants) {
+                FlatSigningProvider dummy;
+                std::optional<CPubKey> pubkey = prov->GetPubKey(0, arg, dummy, read_cache, write_cache);
+                if (!pubkey.has_value()) {
+                    return std::nullopt;
+                }
+                pubkeys.push_back(pubkey.value());
+            }
+            std::sort(pubkeys.begin(), pubkeys.end());
+
+            // Aggregate the pubkey
+            m_aggregate_pubkey = MuSig2AggregatePubkeys(pubkeys);
+            Assert(m_aggregate_pubkey.has_value());
+
+            // Make our pubkey provider
+            if (m_derive != DeriveType::NO || !m_path.empty()) {
+                // Make the synthetic xpub and construct the BIP32PubkeyProvider
+                CExtPubKey extpub;
+                extpub.nDepth = 0;
+                std::memset(extpub.vchFingerprint, 0, 4);
+                extpub.nChild = 0;
+                extpub.chaincode = uint256::FromHex("6589e367712c6200e367717145cb322d76576bc3248959c474f9a602ca878086").value();
+                extpub.pubkey = m_aggregate_pubkey.value();
+
+                m_aggregate_provider = std::make_unique<BIP32PubkeyProvider>(m_expr_index, extpub, m_path, m_derive, /*apostrophe=*/false);
+            } else {
+                m_aggregate_provider = std::make_unique<ConstPubkeyProvider>(m_expr_index, m_aggregate_pubkey.value(), /*xonly=*/false);
+            }
+        }
+
+        // Retrieve all participant pubkeys
+        std::vector<CPubKey> pubkeys;
+        for (const auto& prov : m_participants) {
+            std::optional<CPubKey> pub = prov->GetPubKey(pos, arg, out, read_cache, write_cache);
+            if (!pub) return std::nullopt;
+            pubkeys.emplace_back(*pub);
+        }
+        std::sort(pubkeys.begin(), pubkeys.end());
+
+        CPubKey pubout;
+        if (m_aggregate_provider) {
+            // When we have a cached aggregate key, we are either returning it or deriving from it
+            // Either way, we can passthrough to it's GetPubKey
+            std::optional<CPubKey> pub = m_aggregate_provider->GetPubKey(pos, arg, out, read_cache, write_cache);
+            if (!pub) return std::nullopt;
+            pubout = *pub;
+            out.aggregate_pubkeys.emplace(m_aggregate_pubkey.value(), pubkeys);
+        } else if (IsRangedParticipants()) {
+            // Derive participants and compute new aggregate key
+            std::optional<CPubKey> aggregate_pubkey = MuSig2AggregatePubkeys(pubkeys);
+            if (!aggregate_pubkey) return std::nullopt;
+            pubout = *aggregate_pubkey;
+
+            KeyOriginInfo info;
+            CKeyID keyid = aggregate_pubkey->GetID();
+            std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
+            out.origins.emplace(keyid, std::make_pair(*aggregate_pubkey, info));
+            out.pubkeys.emplace(aggregate_pubkey->GetID(), *aggregate_pubkey);
+            out.aggregate_pubkeys.emplace(pubout, pubkeys);
+        }
+
+        Assert(pubout.IsValid());
+        return pubout;
+    }
+    bool IsRange() const override { return IsRangedDerivation() || IsRangedParticipants(); }
+    // musig() expressions can only be used in tr() contexts which have 32 byte xonly pubkeys
+    size_t GetSize() const override { return 32; }
+
+    std::string ToString(StringType type=StringType::PUBLIC) const override
+    {
+        std::string out = "musig(";
+        for (size_t i = 0; i < m_participants.size(); ++i) {
+            const auto& pubkey = m_participants.at(i);
+            if (i) out += ",";
+            std::string tmp;
+            switch (type) {
+                case StringType::PUBLIC:
+                    tmp = pubkey->ToString();
+                    break;
+                case StringType::COMPAT:
+                    tmp = pubkey->ToString(PubkeyProvider::StringType::COMPAT);
+                    break;
+            }
+            out += tmp;
+        }
+        out += ")";
+        out += FormatHDKeypath(m_path, /*apostrophe=*/true);
+        if (IsRangedDerivation()) {
+            out += "/*";
+        }
+        return out;
+    }
+    bool ToPrivateString(const SigningProvider& arg, std::string& out) const override
+    {
+        bool any_privkeys = false;
+        out = "musig(";
+        for (size_t i = 0; i < m_participants.size(); ++i) {
+            const auto& pubkey = m_participants.at(i);
+            if (i) out += ",";
+            std::string tmp;
+            if (pubkey->ToPrivateString(arg, tmp)) {
+                any_privkeys = true;
+                out += tmp;
+            } else {
+                out += pubkey->ToString();
+            }
+        }
+        out += ")";
+        out += FormatHDKeypath(m_path, /*apostrophe=*/true);
+        if (IsRangedDerivation()) {
+            out += "/*";
+        }
+        if (!any_privkeys) out.clear();
+        return any_privkeys;
+    }
+    bool ToNormalizedString(const SigningProvider& arg, std::string& out, const DescriptorCache* cache = nullptr) const override
+    {
+        out = "musig(";
+        for (size_t i = 0; i < m_participants.size(); ++i) {
+            const auto& pubkey = m_participants.at(i);
+            if (i) out += ",";
+            std::string tmp;
+            if (!pubkey->ToNormalizedString(arg, tmp)) {
+                return false;
+            }
+            out += tmp;
+        }
+        out += ")";
+        out += FormatHDKeypath(m_path, /*apostrophe=*/true);
+        if (IsRangedDerivation()) {
+            out += "/*";
+        }
+        return true;
+    }
+
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
+    {
+        // Get the private keys for all participants
+        // If there is participant derivation, it will be done.
+        // If there is not, then the participant privkeys will be included directly
+        for (const auto& prov : m_participants) {
+            prov->GetPrivKey(pos, arg, out);
+        }
+    }
+    std::optional<CPubKey> GetRootPubKey() const override
+    {
+        return std::nullopt;
+    }
+    std::optional<CExtPubKey> GetRootExtPubKey() const override
+    {
+        return std::nullopt;
+    }
+    std::unique_ptr<PubkeyProvider> Clone() const override
+    {
+        std::vector<std::unique_ptr<PubkeyProvider>> providers;
+        providers.reserve(m_participants.size());
+        for (const std::unique_ptr<PubkeyProvider>& p : m_participants) {
+            providers.emplace_back(p->Clone());
+        }
+        return std::make_unique<MuSigPubkeyProvider>(m_expr_index, std::move(providers), m_path, m_derive);
+    }
+    bool IsBIP32() const override
+    {
+        // musig() can only be a BIP 32 key if all participants are bip32 too
+        bool all_bip32 = true;
+        for (const auto& pk : m_participants) {
+            all_bip32 &= pk->IsBIP32();
+        }
+        return all_bip32;
+    }
+};
+
 /** Base class for all Descriptor implementations. */
 class DescriptorImpl : public Descriptor
 {
@@ -700,16 +930,17 @@ public:
     // NOLINTNEXTLINE(misc-no-recursion)
     bool ExpandHelper(int pos, const SigningProvider& arg, const DescriptorCache* read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache) const
     {
-        std::vector<std::pair<CPubKey, KeyOriginInfo>> entries;
+        FlatSigningProvider subprovider;
-        entries.reserve(m_pubkey_args.size());
+        std::vector<CPubKey> pubkeys;
+        pubkeys.reserve(m_pubkey_args.size());
 
-        // Construct temporary data in `entries`, `subscripts`, and `subprovider` to avoid producing output in case of failure.
+        // Construct temporary data in `pubkeys`, `subscripts`, and `subprovider` to avoid producing output in case of failure.
         for (const auto& p : m_pubkey_args) {
-            entries.emplace_back();
+            std::optional<CPubKey> pubkey = p->GetPubKey(pos, arg, subprovider, read_cache, write_cache);
-            if (!p->GetPubKey(pos, arg, entries.back().first, entries.back().second, read_cache, write_cache)) return false;
+            if (!pubkey) return false;
+            pubkeys.push_back(pubkey.value());
         }
         std::vector<CScript> subscripts;
-        FlatSigningProvider subprovider;
         for (const auto& subarg : m_subdescriptor_args) {
             std::vector<CScript> outscripts;
             if (!subarg->ExpandHelper(pos, arg, read_cache, outscripts, subprovider, write_cache)) return false;
@@ -718,13 +949,6 @@ public:
         }
         out.Merge(std::move(subprovider));
 
-        std::vector<CPubKey> pubkeys;
-        pubkeys.reserve(entries.size());
-        for (auto& entry : entries) {
-            pubkeys.push_back(entry.first);
-            out.origins.emplace(entry.first.GetID(), std::make_pair<CPubKey, KeyOriginInfo>(CPubKey(entry.first), std::move(entry.second)));
-        }
-
         output_scripts = MakeScripts(pubkeys, Span{subscripts}, out);
         return true;
     }
@@ -744,8 +968,7 @@ public:
     {
         for (const auto& p : m_pubkey_args) {
             CKey key;
-            if (!p->GetPrivKey(pos, provider, key)) continue;
+            p->GetPrivKey(pos, provider, out);
-            out.keys.emplace(key.GetPubKey().GetID(), key);
         }
         for (const auto& arg : m_subdescriptor_args) {
             arg->ExpandPrivate(pos, provider, out);
@@ -800,6 +1023,7 @@ public:
         return OutputTypeFromDestination(m_destination);
     }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
     bool ToPrivateString(const SigningProvider& arg, std::string& out) const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override { return GetScriptForDestination(m_destination).size(); }
@@ -827,6 +1051,7 @@ public:
         return OutputTypeFromDestination(dest);
     }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
     bool ToPrivateString(const SigningProvider& arg, std::string& out) const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override { return m_script.size(); }
@@ -855,6 +1080,7 @@ protected:
 public:
     PKDescriptor(std::unique_ptr<PubkeyProvider> prov, bool xonly = false) : DescriptorImpl(Vector(std::move(prov)), "pk"), m_xonly(xonly) {}
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return true; }
 
     std::optional<int64_t> ScriptSize() const override {
         return 1 + (m_xonly ? 32 : m_pubkey_args[0]->GetSize()) + 1;
@@ -884,13 +1110,13 @@ protected:
     std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, Span<const CScript>, FlatSigningProvider& out) const override
     {
         CKeyID id = keys[0].GetID();
-        out.pubkeys.emplace(id, keys[0]);
         return Vector(GetScriptForDestination(PKHash(id)));
     }
 public:
     PKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Vector(std::move(prov)), "pkh") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::LEGACY; }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return true; }
 
     std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 1 + 20 + 1 + 1; }
 
@@ -918,13 +1144,13 @@ protected:
     std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, Span<const CScript>, FlatSigningProvider& out) const override
     {
         CKeyID id = keys[0].GetID();
-        out.pubkeys.emplace(id, keys[0]);
         return Vector(GetScriptForDestination(WitnessV0KeyHash(id)));
     }
 public:
     WPKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Vector(std::move(prov)), "wpkh") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32; }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return true; }
 
     std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 20; }
 
@@ -953,7 +1179,6 @@ protected:
     {
         std::vector<CScript> ret;
         CKeyID id = keys[0].GetID();
-        out.pubkeys.emplace(id, keys[0]);
         ret.emplace_back(GetScriptForRawPubKey(keys[0])); // P2PK
         ret.emplace_back(GetScriptForDestination(PKHash(id))); // P2PKH
         if (keys[0].IsCompressed()) {
@@ -971,6 +1196,7 @@ public:
     {
         return std::make_unique<ComboDescriptor>(m_pubkey_args.at(0)->Clone());
     }
+    bool IsSingleKey() const final { return true; }
 };
 
 /** A parsed multi(...) or sortedmulti(...) descriptor */
@@ -991,6 +1217,7 @@ protected:
 public:
     MultisigDescriptor(int threshold, std::vector<std::unique_ptr<PubkeyProvider>> providers, bool sorted = false) : DescriptorImpl(std::move(providers), sorted ? "sortedmulti" : "multi"), m_threshold(threshold), m_sorted(sorted) {}
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override {
         const auto n_keys = m_pubkey_args.size();
@@ -1042,6 +1269,7 @@ protected:
 public:
     MultiADescriptor(int threshold, std::vector<std::unique_ptr<PubkeyProvider>> providers, bool sorted = false) : DescriptorImpl(std::move(providers), sorted ? "sortedmulti_a" : "multi_a"), m_threshold(threshold), m_sorted(sorted) {}
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override {
         const auto n_keys = m_pubkey_args.size();
@@ -1088,6 +1316,7 @@ public:
         return OutputType::LEGACY;
     }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return m_subdescriptor_args[0]->IsSingleKey(); }
 
     std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 20 + 1; }
 
@@ -1129,6 +1358,7 @@ public:
     WSHDescriptor(std::unique_ptr<DescriptorImpl> desc) : DescriptorImpl({}, std::move(desc), "wsh") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32; }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return m_subdescriptor_args[0]->IsSingleKey(); }
 
     std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 32; }
 
@@ -1175,7 +1405,6 @@ protected:
         builder.Finalize(xpk);
         WitnessV1Taproot output = builder.GetOutput();
         out.tr_trees[output] = builder;
-        out.pubkeys.emplace(keys[0].GetID(), keys[0]);
         return Vector(GetScriptForDestination(output));
     }
     bool ToStringSubScriptHelper(const SigningProvider* arg, std::string& ret, const StringType type, const DescriptorCache* cache = nullptr) const override
@@ -1207,6 +1436,7 @@ public:
     }
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32M; }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 32; }
 
@@ -1334,6 +1564,7 @@ public:
 
     bool IsSolvable() const override { return true; }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override { return m_node->ScriptSize(); }
 
@@ -1373,6 +1604,7 @@ public:
     RawTRDescriptor(std::unique_ptr<PubkeyProvider> output_key) : DescriptorImpl(Vector(std::move(output_key)), "rawtr") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32M; }
     bool IsSingleType() const final { return true; }
+    bool IsSingleKey() const final { return false; }
 
     std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 32; }
 
@@ -1402,14 +1634,19 @@ enum class ParseScriptContext {
     P2WPKH,  //!< Inside wpkh() (no script, pubkey only)
     P2WSH,   //!< Inside wsh() (script becomes v0 witness script)
     P2TR,    //!< Inside tr() (either internal key, or BIP342 script leaf)
+    MUSIG,   //!< Inside musig() (implies P2TR, cannot have nested musig())
 };
 
-std::optional<uint32_t> ParseKeyPathNum(Span<const char> elem, bool& apostrophe, std::string& error)
+std::optional<uint32_t> ParseKeyPathNum(Span<const char> elem, bool& apostrophe, std::string& error, bool allow_hardened)
 {
     bool hardened = false;
     if (elem.size() > 0) {
         const char last = elem[elem.size() - 1];
         if (last == '\'' || last == 'h') {
+            if (!allow_hardened) {
+                error = "cannot have hardened derivation steps";
+                return std::nullopt;
+            }
             elem = elem.first(elem.size() - 1);
             hardened = true;
             apostrophe = last == '\'';
@@ -1437,7 +1674,7 @@ std::optional<uint32_t> ParseKeyPathNum(Span<const char> elem, bool& apostrophe,
  * @param[in] allow_multipath Allows the parsed path to use the multipath specifier
  * @returns false if parsing failed
  **/
-[[nodiscard]] bool ParseKeyPath(const std::vector<Span<const char>>& split, std::vector<KeyPath>& out, bool& apostrophe, std::string& error, bool allow_multipath)
+[[nodiscard]] bool ParseKeyPath(const std::vector<Span<const char>>& split, std::vector<KeyPath>& out, bool& apostrophe, std::string& error, bool allow_multipath, bool allow_hardened = true)
 {
     KeyPath path;
     std::optional<size_t> multipath_segment_index;
@@ -1466,7 +1703,7 @@ std::optional<uint32_t> ParseKeyPathNum(Span<const char> elem, bool& apostrophe,
             }
 
             for (const auto& num : nums) {
-                const auto& op_num = ParseKeyPathNum(num, apostrophe, error);
+                const auto& op_num = ParseKeyPathNum(num, apostrophe, error, allow_hardened);
                 if (!op_num) return false;
                 auto [_, inserted] = seen_multipath.insert(*op_num);
                 if (!inserted) {
@@ -1479,7 +1716,7 @@ std::optional<uint32_t> ParseKeyPathNum(Span<const char> elem, bool& apostrophe,
             path.emplace_back(); // Placeholder for multipath segment
             multipath_segment_index = path.size()-1;
         } else {
-            const auto& op_num = ParseKeyPathNum(elem, apostrophe, error);
+            const auto& op_num = ParseKeyPathNum(elem, apostrophe, error, allow_hardened);
             if (!op_num) return false;
             path.emplace_back(*op_num);
         }
@@ -1578,9 +1815,152 @@ std::vector<std::unique_ptr<PubkeyProvider>> ParsePubkeyInner(uint32_t key_exp_i
 }
 
 /** Parse a public key including origin information (if enabled). */
-std::vector<std::unique_ptr<PubkeyProvider>> ParsePubkey(uint32_t key_exp_index, const Span<const char>& sp, ParseScriptContext ctx, FlatSigningProvider& out, std::string& error)
+// NOLINTNEXTLINE(misc-no-recursion)
+std::vector<std::unique_ptr<PubkeyProvider>> ParsePubkey(uint32_t& key_exp_index, const Span<const char>& sp, ParseScriptContext ctx, FlatSigningProvider& out, std::string& error)
 {
     std::vector<std::unique_ptr<PubkeyProvider>> ret;
+
+    using namespace script;
+
+    // musig cannot be nested inside of an origin
+    Span<const char> span = sp;
+    if (Const("musig(", span, /*skip=*/false)) {
+        if (ctx != ParseScriptContext::P2TR) {
+            error = "musig() is only allowed in tr()";
+            return {};
+        }
+
+        auto split = Split(span, ')');
+        if (split.size() > 2) {
+            error = "Too many ')' in musig() expression";
+            return {};
+        }
+        // Make a span that includes the end parentheses so that Expr is happy
+        Span<const char> sp_musig(split.at(0).begin(), split.at(0).end() + 1);
+
+        auto expr = Expr(sp_musig);
+        if (!Func("musig", expr)) {
+            error = "Invalid musig() expression";
+            return {};
+        }
+
+        // Parse the participant pubkeys
+        bool any_ranged = false;
+        bool all_bip32 = true;
+        std::vector<std::vector<std::unique_ptr<PubkeyProvider>>> providers;
+        bool first = true;
+        size_t max_providers_len = 0;
+        while (expr.size()) {
+            if (!first && !Const(",", expr)) {
+                error = strprintf("musig(): expected ',', got '%c'", expr[0]);
+                return {};
+            }
+            first = false;
+            auto arg = Expr(expr);
+            auto pk = ParsePubkey(key_exp_index, arg, ParseScriptContext::MUSIG, out, error);
+            if (pk.empty()) {
+                error = strprintf("musig(): %s", error);
+                return {};
+            }
+
+            any_ranged |= pk.at(0)->IsRange();
+            all_bip32 &= pk.at(0)->IsBIP32();
+
+            max_providers_len = std::max(max_providers_len, pk.size());
+
+            providers.emplace_back(std::move(pk));
+            key_exp_index++;
+        }
+        if (first) {
+            error = "musig(): Must contain key expressions";
+            return {};
+        }
+
+        // Parse any derivation
+        DeriveType deriv_type = DeriveType::NO;
+        std::vector<KeyPath> paths;
+        if (split.size() == 2 && Const("/", split.at(1), /*skip=*/false)) {
+            if (!all_bip32) {
+                error = "musig(): Ranged musig() requires all participants to be xpubs";
+                return {};
+            }
+            auto deriv_split = Split(split.at(1), '/');
+            if (std::ranges::equal(deriv_split.back(), Span{"*"}.first(1))) {
+                deriv_split.pop_back();
+                deriv_type = DeriveType::UNHARDENED;
+                if (any_ranged) {
+                    error = "musig(): Cannot have ranged participant keys if musig() is also ranged";
+                    return {};
+                }
+            } else if (std::ranges::equal(deriv_split.back(), Span{"*'"}.first(2)) || std::ranges::equal(deriv_split.back(), Span{"*h"}.first(2))) {
+                error = "musig(): Cannot have hardened child derivation";
+                return {};
+            }
+            bool dummy = false;
+            if (!ParseKeyPath(deriv_split, paths, dummy, error, /*allow_multipath=*/true, /*allow_hardened=*/false)) {
+                error = "musig(): " + error;
+                return {};
+            }
+        } else {
+            paths.emplace_back();
+        }
+
+        // Makes sure that all providers vectors in providers are the given length, or exactly length 1
+        // Length 1 vectors have the single provider cloned until it matches the given length.
+        const auto& clone_providers = [&providers](size_t length) -> bool {
+            for (auto& vec : providers) {
+                if (vec.size() == 1) {
+                    for (size_t i = 1; i < length; ++i) {
+                        vec.emplace_back(vec.at(0)->Clone());
+                    }
+                } else if (vec.size() != length) {
+                    return false;
+                }
+            }
+            return true;
+        };
+
+        // Emplace the final MuSigPubkeyProvider into ret with the pubkey providers from the specified provider vectors index
+        // and the path from the specified path index
+        const auto& emplace_final_provider = [&ret, &key_exp_index, &deriv_type, &paths, &providers](size_t vec_idx, size_t path_idx) -> void {
+            KeyPath& path = paths.at(path_idx);
+            std::vector<std::unique_ptr<PubkeyProvider>> pubs;
+            pubs.reserve(providers.size());
+            for (auto& vec : providers) {
+                pubs.emplace_back(std::move(vec.at(vec_idx)));
+            }
+            ret.emplace_back(std::make_unique<MuSigPubkeyProvider>(key_exp_index, std::move(pubs), path, deriv_type));
+        };
+
+        if (max_providers_len > 1 && paths.size() > 1) {
+            error = "musig(): Cannot have multipath participant keys if musig() is also multipath";
+            return {};
+        } else if (max_providers_len > 1) {
+            if (!clone_providers(max_providers_len)) {
+                error = strprintf("musig(): Multipath derivation paths have mismatched lengths");
+                return {};
+            }
+            for (size_t i = 0; i < max_providers_len; ++i) {
+                // Final MuSigPubkeyProvider use participant pubkey providers at each multipath position, and the first (and only) path
+                emplace_final_provider(i, 0);
+            }
+        } else if (paths.size() > 1) {
+            // All key provider vectors should be length 1. Clone them until they have the same length as paths
+            if (!clone_providers(paths.size())) {
+                error = "musig(): Multipath derivation path with multipath participants is disallowed"; // This error is unreachable due to earlier check
+                return {};
+            }
+            for (size_t i = 0; i < paths.size(); ++i) {
+                // Final MuSigPubkeyProvider uses cloned participant pubkey providers, and the multipath derivation paths
+                emplace_final_provider(i, i);
+            }
+        } else {
+            // No multipath derivation MuSigPubkeyProvider uses the first (and only) participant pubkey providers, and the first (and only) path
+            emplace_final_provider(0, 0);
+        }
+        return ret;
+    }
+
     auto origin_split = Split(sp, ']');
     if (origin_split.size() > 2) {
         error = "Multiple ']' characters found for a single pubkey";
@@ -1691,7 +2071,8 @@ struct KeyParser {
     {
         assert(m_out);
         Key key = m_keys.size();
-        auto pk = ParsePubkey(m_offset + key, {&*begin, &*end}, ParseContext(), *m_out, m_key_parsing_error);
+        uint32_t exp_index = m_offset + key;
+        auto pk = ParsePubkey(exp_index, {&*begin, &*end}, ParseContext(), *m_out, m_key_parsing_error);
         if (pk.empty()) return {};
         m_keys.emplace_back(std::move(pk));
         return key;

src/script/descriptor.h

@@ -111,6 +111,11 @@ struct Descriptor {
     /** Whether this descriptor will return one scriptPubKey or multiple (aka is or is not combo) */
     virtual bool IsSingleType() const = 0;
 
+    /** Whether this descriptor only produces single key scripts (i.e. pk(), pkh(), wpkh(), sh() and wsh() nested of those, and combo()
+     *  TODO: Remove this method once legacy wallets are removed as it is only necessary for importmulti.
+     */
+    virtual bool IsSingleKey() const = 0;
+
     /** Convert the descriptor to a private string. This fails if the provided provider does not have the relevant private keys. */
     virtual bool ToPrivateString(const SigningProvider& provider, std::string& out) const = 0;
 

src/script/parsing.cpp

@@ -12,10 +12,10 @@
 
 namespace script {
 
-bool Const(const std::string& str, Span<const char>& sp)
+bool Const(const std::string& str, Span<const char>& sp, bool skip)
 {
     if ((size_t)sp.size() >= str.size() && std::equal(str.begin(), str.end(), sp.begin())) {
-        sp = sp.subspan(str.size());
+        if (skip) sp = sp.subspan(str.size());
         return true;
     }
     return false;

src/script/parsing.h

@@ -13,10 +13,10 @@ namespace script {
 
 /** Parse a constant.
  *
- * If sp's initial part matches str, sp is updated to skip that part, and true is returned.
+ * If sp's initial part matches str, sp is optionally updated to skip that part, and true is returned.
  * Otherwise sp is unmodified and false is returned.
  */
-bool Const(const std::string& str, Span<const char>& sp);
+bool Const(const std::string& str, Span<const char>& sp, bool skip = true);
 
 /** Parse a function call.
  *

src/script/script.cpp

@@ -238,6 +238,13 @@ bool CScript::IsPayToWitnessScriptHash() const
             (*this)[1] == 0x20);
 }
 
+bool CScript::IsPayToTaproot() const
+{
+    return (this->size() == 34 &&
+            (*this)[0] == OP_1 &&
+            (*this)[1] == 0x20);
+}
+
 // A witness program is any valid CScript that consists of a 1-byte push opcode
 // followed by a data push between 2 and 40 bytes.
 bool CScript::IsWitnessProgram(int& version, std::vector<unsigned char>& program) const

src/script/script.h

@@ -556,6 +556,8 @@ public:
     bool IsPayToWitnessScriptHash() const;
     bool IsWitnessProgram(int& version, std::vector<unsigned char>& program) const;
 
+    bool IsPayToTaproot() const;
+
     /** Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical). */
     bool IsPushOnly(const_iterator pc) const;
     bool IsPushOnly() const;

src/script/sign.cpp

@@ -7,8 +7,10 @@
 
 #include <consensus/amount.h>
 #include <key.h>
+#include <musig.h>
 #include <policy/policy.h>
 #include <primitives/transaction.h>
+#include <random.h>
 #include <script/keyorigin.h>
 #include <script/miniscript.h>
 #include <script/script.h>
@@ -59,17 +61,14 @@ bool MutableTransactionSignatureCreator::CreateSig(const SigningProvider& provid
     return true;
 }
 
-bool MutableTransactionSignatureCreator::CreateSchnorrSig(const SigningProvider& provider, std::vector<unsigned char>& sig, const XOnlyPubKey& pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion) const
+std::optional<uint256> MutableTransactionSignatureCreator::ComputeSchnorrSignatureHash(const uint256* leaf_hash, SigVersion sigversion) const
 {
     assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT);
 
-    CKey key;
-    if (!provider.GetKeyByXOnly(pubkey, key)) return false;
-
     // BIP341/BIP342 signing needs lots of precomputed transaction data. While some
     // (non-SIGHASH_DEFAULT) sighash modes exist that can work with just some subset
     // of data present, for now, only support signing when everything is provided.
-    if (!m_txdata || !m_txdata->m_bip341_taproot_ready || !m_txdata->m_spent_outputs_ready) return false;
+    if (!m_txdata || !m_txdata->m_bip341_taproot_ready || !m_txdata->m_spent_outputs_ready) return std::nullopt;
 
     ScriptExecutionData execdata;
     execdata.m_annex_init = true;
@@ -77,19 +76,134 @@ bool MutableTransactionSignatureCreator::CreateSchnorrSig(const SigningProvider&
     if (sigversion == SigVersion::TAPSCRIPT) {
         execdata.m_codeseparator_pos_init = true;
         execdata.m_codeseparator_pos = 0xFFFFFFFF; // Only support non-OP_CODESEPARATOR BIP342 signing for now.
-        if (!leaf_hash) return false; // BIP342 signing needs leaf hash.
+        if (!leaf_hash) return std::nullopt; // BIP342 signing needs leaf hash.
         execdata.m_tapleaf_hash_init = true;
         execdata.m_tapleaf_hash = *leaf_hash;
     }
     uint256 hash;
-    if (!SignatureHashSchnorr(hash, execdata, m_txto, nIn, nHashType, sigversion, *m_txdata, MissingDataBehavior::FAIL)) return false;
+    if (!SignatureHashSchnorr(hash, execdata, m_txto, nIn, nHashType, sigversion, *m_txdata, MissingDataBehavior::FAIL)) return std::nullopt;
+    return hash;
+}
+
+bool MutableTransactionSignatureCreator::CreateSchnorrSig(const SigningProvider& provider, std::vector<unsigned char>& sig, const XOnlyPubKey& pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion) const
+{
+    assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT);
+
+    CKey key;
+    if (!provider.GetKeyByXOnly(pubkey, key)) return false;
+
+    std::optional<uint256> hash = ComputeSchnorrSignatureHash(leaf_hash, sigversion);
+    if (!hash.has_value()) return false;
+
     sig.resize(64);
     // Use uint256{} as aux_rnd for now.
-    if (!key.SignSchnorr(hash, sig, merkle_root, {})) return false;
+    if (!key.SignSchnorr(*hash, sig, merkle_root, {})) return false;
     if (nHashType) sig.push_back(nHashType);
     return true;
 }
 
+bool MutableTransactionSignatureCreator::CreateMuSig2AggregateSig(const std::vector<CPubKey>& participants, std::vector<uint8_t>& sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const
+{
+    assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT);
+    if (!participants.size()) return false;
+
+    // Retrieve pubnonces and partial sigs
+    auto this_leaf_aggkey = std::make_pair(script_pubkey, leaf_hash ? *leaf_hash : uint256());
+    auto pubnonce_it = sigdata.musig2_pubnonces.find(this_leaf_aggkey);
+    if (pubnonce_it == sigdata.musig2_pubnonces.end()) return false;
+    const std::map<CPubKey, std::vector<uint8_t>>& pubnonces = pubnonce_it->second;
+    auto partial_sigs_it = sigdata.musig2_partial_sigs.find(this_leaf_aggkey);
+    if (partial_sigs_it == sigdata.musig2_partial_sigs.end()) return false;
+    const std::map<CPubKey, uint256>& partial_sigs = partial_sigs_it->second;
+
+    // Check if enough pubnonces and partial sigs
+    if (pubnonces.size() != participants.size()) return false;
+    if (partial_sigs.size() != participants.size()) return false;
+
+    // Compute sighash
+    std::optional<uint256> sighash = ComputeSchnorrSignatureHash(leaf_hash, sigversion);
+    if (!sighash.has_value()) return false;
+
+    std::optional<std::vector<uint8_t>> res = ::CreateMuSig2AggregateSig(participants, aggregate_pubkey, tweaks, *sighash, pubnonces, partial_sigs);
+    if (!res) return false;
+    sig = res.value();
+    if (nHashType) sig.push_back(nHashType);
+
+    return true;
+}
+
+bool MutableTransactionSignatureCreator::CreateMuSig2PartialSig(const SigningProvider& provider, uint256& partial_sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const
+{
+    assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT);
+
+    // Retrieve private key
+    CKey key;
+    if (!provider.GetKey(part_pubkey.GetID(), key)) return false;
+
+    // Retrieve participant pubkeys
+    std::vector<CPubKey> pubkeys = provider.GetAggregateParticipantPubkeys(aggregate_pubkey);
+    if (!pubkeys.size()) return false;
+
+    // Retrieve pubnonces
+    auto this_leaf_aggkey = std::make_pair(script_pubkey, leaf_hash ? *leaf_hash : uint256());
+    auto pubnonce_it = sigdata.musig2_pubnonces.find(this_leaf_aggkey);
+    if (pubnonce_it == sigdata.musig2_pubnonces.end()) return false;
+    const std::map<CPubKey, std::vector<uint8_t>>& pubnonces = pubnonce_it->second;
+
+    // Check if enough pubnonces
+    if (pubnonces.size() != pubkeys.size()) return false;
+
+    // Compute sighash
+    std::optional<uint256> sighash = ComputeSchnorrSignatureHash(leaf_hash, sigversion);
+    if (!sighash.has_value()) return false;
+
+    // Retrieve the secnonce
+    HashWriter hasher;
+    hasher << script_pubkey << part_pubkey << *sighash;
+    uint256 session_id = hasher.GetSHA256();
+    std::optional<std::reference_wrapper<MuSig2SecNonce>> secnonce = provider.GetMuSig2SecNonce(session_id);
+    if (!secnonce || !secnonce->get().IsValid()) return false;
+
+    // Compute the sig
+    std::optional<uint256> sig = key.CreateMuSig2PartialSig(*sighash, aggregate_pubkey, pubkeys, pubnonces, *secnonce, tweaks);
+    if (!sig) return false;
+    partial_sig = std::move(*sig);
+
+    // Delete the secnonce now that we're done with it
+    provider.DeleteMuSig2Session(session_id);
+
+    return true;
+}
+
+std::vector<uint8_t> MutableTransactionSignatureCreator::CreateMuSig2Nonce(const SigningProvider& provider, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion, const SignatureData& sigdata) const
+{
+    assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT);
+
+    // Retrieve the private key
+    CKey key;
+    if (!provider.GetKey(part_pubkey.GetID(), key)) return {};
+
+    // Retrieve participant pubkeys
+    std::vector<CPubKey> pubkeys = provider.GetAggregateParticipantPubkeys(aggregate_pubkey);
+    if (!pubkeys.size()) return {};
+
+    // Compute sighash
+    std::optional<uint256> sighash = ComputeSchnorrSignatureHash(leaf_hash, sigversion);
+    if (!sighash.has_value()) return {};
+
+    MuSig2SecNonce secnonce;
+    std::vector<uint8_t> out = key.CreateMuSig2Nonce(secnonce, *sighash, aggregate_pubkey, pubkeys);
+    if (out.empty()) return {};
+
+    // Store the secnonce in the SigningProvider
+    HashWriter hasher;
+    hasher << script_pubkey << part_pubkey << *sighash;
+    uint256 id = hasher.GetSHA256();
+    provider.SetMuSig2SecNonce(id, std::move(secnonce));
+
+    return out;
+}
+
 static bool GetCScript(const SigningProvider& provider, const SignatureData& sigdata, const CScriptID& scriptid, CScript& script)
 {
     if (provider.GetCScript(scriptid, script)) {
@@ -169,12 +283,94 @@ static bool CreateTaprootScriptSig(const BaseSignatureCreator& creator, Signatur
         sig_out = it->second;
         return true;
     }
+
     if (creator.CreateSchnorrSig(provider, sig_out, pubkey, &leaf_hash, nullptr, sigversion)) {
         sigdata.taproot_script_sigs[lookup_key] = sig_out;
+    } else {
+        auto misc_pk_it = sigdata.taproot_misc_pubkeys.find(pubkey);
+        if (misc_pk_it != sigdata.taproot_misc_pubkeys.end()) {
+            info = misc_pk_it->second.second;
+        }
+
+        for (const auto& [agg_pub, part_pks] : sigdata.musig2_pubkeys) {
+            if (part_pks.empty()) continue;
+
+            // Fill participant derivation path info
+            for (const auto& part_pk : part_pks) {
+                KeyOriginInfo part_info;
+                if (provider.GetKeyOrigin(part_pk.GetID(), part_info)) {
+                    XOnlyPubKey xonly_part(part_pk);
+                    auto it = sigdata.taproot_misc_pubkeys.find(xonly_part);
+                    if (it == sigdata.taproot_misc_pubkeys.end()) {
+                        sigdata.taproot_misc_pubkeys.emplace(xonly_part, std::make_pair(std::set<uint256>({leaf_hash}), part_info));
+                    } else {
+                        it->second.first.insert(leaf_hash);
+                    }
+                }
+            }
+
+            std::vector<std::pair<uint256, bool>> tweaks;
+            CPubKey plain_pub = agg_pub;
+            if (XOnlyPubKey(agg_pub) != pubkey) {
+                if (info.path.size() > 0) {
+                    // Compute and compare fingerprint
+                    CKeyID keyid = agg_pub.GetID();
+                    if (std::memcmp(keyid.data(), info.fingerprint, sizeof(info.fingerprint)) != 0) {
+                        continue;
+                    }
+                    // Get the BIP32 derivation tweaks
+                    CExtPubKey extpub;
+                    extpub.nDepth = 0;
+                    std::memset(extpub.vchFingerprint, 0, 4);
+                    extpub.nChild = 0;
+                    extpub.chaincode = uint256::FromHex("6589e367712c6200e367717145cb322d76576bc3248959c474f9a602ca878086").value();
+                    extpub.pubkey = agg_pub;
+                    for (const int i : info.path) {
+                        auto& [tweak, xonly] = tweaks.emplace_back();
+                        xonly = false;
+                        if (!extpub.Derive(extpub, i, tweak)) {
+                            return false;
+                        }
+                    }
+                    Assert(XOnlyPubKey(extpub.pubkey) == pubkey);
+                    plain_pub = extpub.pubkey;
+                } else {
+                    continue;
+                }
+            }
+
+            // We know this is musig, try musig signing
+            // First try to aggregate
+            if (creator.CreateMuSig2AggregateSig(part_pks, sig_out, agg_pub, plain_pub, &leaf_hash, tweaks, sigversion, sigdata)) {
+                sigdata.taproot_script_sigs[lookup_key] = sig_out;
                 return true;
             }
+            // Cannot aggregate, try making partial sigs for every participant
+            auto pub_key_leaf_hash = std::make_pair(plain_pub, leaf_hash);
+            for (const CPubKey& part_pk : part_pks) {
+                uint256 partial_sig;
+                if (creator.CreateMuSig2PartialSig(provider, partial_sig, agg_pub, plain_pub, part_pk, &leaf_hash, tweaks, sigversion, sigdata) && Assume(!partial_sig.IsNull())) {
+                    sigdata.musig2_partial_sigs[pub_key_leaf_hash].emplace(part_pk, partial_sig);
+                }
+            }
+            // If there are any partial signatures, exit early
+            auto partial_sigs_it = sigdata.musig2_partial_sigs.find(pub_key_leaf_hash);
+            if (partial_sigs_it != sigdata.musig2_partial_sigs.end() && !partial_sigs_it->second.empty()) {
                 return false;
             }
+            // No partial sigs, try to make pubnonces
+            std::map<CPubKey, std::vector<uint8_t>>& pubnonces = sigdata.musig2_pubnonces[pub_key_leaf_hash];
+            for (const CPubKey& part_pk : part_pks) {
+                if (pubnonces.contains(part_pk)) continue;
+                std::vector<uint8_t> pubnonce = creator.CreateMuSig2Nonce(provider, agg_pub, plain_pub, part_pk, &leaf_hash, nullptr, sigversion, sigdata);
+                if (pubnonce.empty()) continue;
+                pubnonces[part_pk] = std::move(pubnonce);
+            }
+        }
+    }
+
+    return sigdata.taproot_script_sigs.contains(lookup_key);
+}
 
 template<typename M, typename K, typename V>
 miniscript::Availability MsLookupHelper(const M& map, const K& key, V& value)
@@ -342,27 +538,133 @@ static bool SignTaproot(const SigningProvider& provider, const BaseSignatureCrea
     if (provider.GetTaprootBuilder(output, builder)) {
         sigdata.tr_builder = builder;
     }
+    if (auto agg_keys = provider.GetAllAggregateParticipantPubkeys(); !agg_keys.empty()) {
+        sigdata.musig2_pubkeys.merge(agg_keys);
+    }
+
 
     // Try key path spending.
     {
-        KeyOriginInfo info;
+        KeyOriginInfo internal_key_info;
-        if (provider.GetKeyOriginByXOnly(sigdata.tr_spenddata.internal_key, info)) {
+        if (provider.GetKeyOriginByXOnly(sigdata.tr_spenddata.internal_key, internal_key_info)) {
             auto it = sigdata.taproot_misc_pubkeys.find(sigdata.tr_spenddata.internal_key);
             if (it == sigdata.taproot_misc_pubkeys.end()) {
-                sigdata.taproot_misc_pubkeys.emplace(sigdata.tr_spenddata.internal_key, std::make_pair(std::set<uint256>(), info));
+                sigdata.taproot_misc_pubkeys.emplace(sigdata.tr_spenddata.internal_key, std::make_pair(std::set<uint256>(), internal_key_info));
             }
         }
 
+        KeyOriginInfo output_key_info;
+        if (provider.GetKeyOriginByXOnly(output, output_key_info)) {
+            auto it = sigdata.taproot_misc_pubkeys.find(output);
+            if (it == sigdata.taproot_misc_pubkeys.end()) {
+                sigdata.taproot_misc_pubkeys.emplace(output, std::make_pair(std::set<uint256>(), output_key_info));
+            }
+        }
+
+        auto make_keypath_sig = [&](const XOnlyPubKey& pk, const uint256* merkle_root) {
             std::vector<unsigned char> sig;
-        if (sigdata.taproot_key_path_sig.size() == 0) {
+            if (creator.CreateSchnorrSig(provider, sig, pk, nullptr, merkle_root, SigVersion::TAPROOT)) {
-            if (creator.CreateSchnorrSig(provider, sig, sigdata.tr_spenddata.internal_key, nullptr, &sigdata.tr_spenddata.merkle_root, SigVersion::TAPROOT)) {
                 sigdata.taproot_key_path_sig = sig;
+            } else {
+                // Lookup derivation paths for this key
+                KeyOriginInfo info;
+                auto misc_pk_it = sigdata.taproot_misc_pubkeys.find(pk);
+                if (misc_pk_it != sigdata.taproot_misc_pubkeys.end()) {
+                    info = misc_pk_it->second.second;
+                }
+
+                for (const auto& [agg_pub, part_pks] : sigdata.musig2_pubkeys) {
+                    if (part_pks.empty()) continue;
+
+                    // Fill participant derivation path info
+                    for (const auto& part_pk : part_pks) {
+                        KeyOriginInfo info;
+                        if (provider.GetKeyOrigin(part_pk.GetID(), info)) {
+                            XOnlyPubKey xonly_part(part_pk);
+                            auto it = sigdata.taproot_misc_pubkeys.find(xonly_part);
+                            if (it == sigdata.taproot_misc_pubkeys.end()) {
+                                sigdata.taproot_misc_pubkeys.emplace(xonly_part, std::make_pair(std::set<uint256>(), info));
                             }
                         }
-        if (sigdata.taproot_key_path_sig.size() == 0) {
+                    }
-            if (creator.CreateSchnorrSig(provider, sig, output, nullptr, nullptr, SigVersion::TAPROOT)) {
+
+                    std::vector<std::pair<uint256, bool>> tweaks;
+                    CPubKey plain_pub = agg_pub;
+                    if (XOnlyPubKey(agg_pub) != pk) {
+                        if (info.path.size() > 0) {
+                            // Compute and compare fingerprint
+                            CKeyID keyid = agg_pub.GetID();
+                            if (!std::equal(info.fingerprint, info.fingerprint + sizeof(info.fingerprint), keyid.data())) {
+                                continue;
+                            }
+                            // Get the BIP32 derivation tweaks
+                            CExtPubKey extpub;
+                            extpub.nDepth = 0;
+                            std::memset(extpub.vchFingerprint, 0, 4);
+                            extpub.nChild = 0;
+                            extpub.chaincode = uint256::FromHex("6589e367712c6200e367717145cb322d76576bc3248959c474f9a602ca878086").value();
+                            extpub.pubkey = agg_pub;
+                            for (const int i : info.path) {
+                                auto& [t, xonly] = tweaks.emplace_back();
+                                xonly = false;
+                                if (!extpub.Derive(extpub, i, t)) {
+                                    return;
+                                }
+                            }
+                            Assert(XOnlyPubKey(extpub.pubkey) == pk);
+                            plain_pub = extpub.pubkey;
+                        } else {
+                            continue;
+                        }
+                    }
+
+                    // Add the merkle root tweak
+                    if (merkle_root) {
+                        tweaks.emplace_back(pk.ComputeTapTweakHash(merkle_root->IsNull() ? nullptr : merkle_root), true);
+                        std::optional<std::pair<XOnlyPubKey, bool>> tweaked = pk.CreateTapTweak(merkle_root->IsNull() ? nullptr : merkle_root);
+                        if (!Assume(tweaked)) return;
+                        plain_pub = tweaked->first.GetCPubKeys().at(tweaked->second ? 1 : 0);
+                    }
+
+                    // We know this is musig, try musig signing
+                    // First try to aggregate
+                    if (creator.CreateMuSig2AggregateSig(part_pks, sig, agg_pub, plain_pub, nullptr, tweaks, SigVersion::TAPROOT, sigdata)) {
                         sigdata.taproot_key_path_sig = sig;
+                        return;
                     }
+                    // Cannot aggregate, try making partial sigs for every participant
+                    auto pub_key_leaf_hash = std::make_pair(plain_pub, uint256());
+                    for (const CPubKey& part_pk : part_pks) {
+                        uint256 partial_sig;
+                        if (creator.CreateMuSig2PartialSig(provider, partial_sig, agg_pub, plain_pub, part_pk, nullptr, tweaks, SigVersion::TAPROOT, sigdata) && Assume(!partial_sig.IsNull())) {
+                            sigdata.musig2_partial_sigs[pub_key_leaf_hash].emplace(part_pk, partial_sig);
+                        }
+                    }
+                    // If there are any partial signatures, exit early
+                    auto partial_sigs_it = sigdata.musig2_partial_sigs.find(pub_key_leaf_hash);
+                    if (partial_sigs_it != sigdata.musig2_partial_sigs.end() && !partial_sigs_it->second.empty()) {
+                        return;
+                    }
+                    // No partial sigs, try to make pubnonces
+                    std::map<CPubKey, std::vector<uint8_t>>& pubnonces = sigdata.musig2_pubnonces[pub_key_leaf_hash];
+                    for (const CPubKey& part_pk : part_pks) {
+                        if (pubnonces.contains(part_pk)) continue;
+                        std::vector<uint8_t> pubnonce = creator.CreateMuSig2Nonce(provider, agg_pub, plain_pub, part_pk, nullptr, merkle_root, SigVersion::TAPROOT, sigdata);
+                        if (pubnonce.empty()) continue;
+                        pubnonces[part_pk] = std::move(pubnonce);
+                    }
+                    break;
+                }
+            }
+        };
+
+        // First try signing with internal key
+        if (sigdata.taproot_key_path_sig.size() == 0) {
+            make_keypath_sig(sigdata.tr_spenddata.internal_key, &sigdata.tr_spenddata.merkle_root);
+        }
+        // Try signing with output key if still no signature
+        if (sigdata.taproot_key_path_sig.size() == 0) {
+            make_keypath_sig(output, nullptr);
         }
         if (sigdata.taproot_key_path_sig.size()) {
             result = Vector(sigdata.taproot_key_path_sig);
@@ -737,6 +1039,22 @@ public:
         sig.assign(64, '\000');
         return true;
     }
+    bool CreateMuSig2AggregateSig(const std::vector<CPubKey>& participants, std::vector<uint8_t>& sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const override
+    {
+        sig.assign(64, '\000');
+        return true;
+    }
+    bool CreateMuSig2PartialSig(const SigningProvider& provider, uint256& partial_sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const override
+    {
+        partial_sig = uint256::ONE;
+        return true;
+    }
+    std::vector<uint8_t> CreateMuSig2Nonce(const SigningProvider& provider, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion, const SignatureData& sigdata) const override
+    {
+        std::vector<uint8_t> out;
+        out.assign(66, '\000');
+        return out;
+    }
 };
 
 }

src/script/sign.h

@@ -23,6 +23,7 @@ class SigningProvider;
 
 struct bilingual_str;
 struct CMutableTransaction;
+struct SignatureData;
 
 /** Interface for signature creators. */
 class BaseSignatureCreator {
@@ -33,6 +34,9 @@ public:
     /** Create a singular (non-script) signature. */
     virtual bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const =0;
     virtual bool CreateSchnorrSig(const SigningProvider& provider, std::vector<unsigned char>& sig, const XOnlyPubKey& pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion) const =0;
+    virtual bool CreateMuSig2AggregateSig(const std::vector<CPubKey>& participants, std::vector<uint8_t>& sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const =0;
+    virtual bool CreateMuSig2PartialSig(const SigningProvider& provider, uint256& partial_sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const =0;
+    virtual std::vector<uint8_t> CreateMuSig2Nonce(const SigningProvider& provider, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion, const SignatureData& sigdata) const =0;
 };
 
 /** A signature creator for transactions. */
@@ -45,12 +49,17 @@ class MutableTransactionSignatureCreator : public BaseSignatureCreator
     const MutableTransactionSignatureChecker checker;
     const PrecomputedTransactionData* m_txdata;
 
+    std::optional<uint256> ComputeSchnorrSignatureHash(const uint256* leaf_hash, SigVersion sigversion) const;
+
 public:
     MutableTransactionSignatureCreator(const CMutableTransaction& tx LIFETIMEBOUND, unsigned int input_idx, const CAmount& amount, int hash_type);
     MutableTransactionSignatureCreator(const CMutableTransaction& tx LIFETIMEBOUND, unsigned int input_idx, const CAmount& amount, const PrecomputedTransactionData* txdata, int hash_type);
     const BaseSignatureChecker& Checker() const override { return checker; }
     bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
     bool CreateSchnorrSig(const SigningProvider& provider, std::vector<unsigned char>& sig, const XOnlyPubKey& pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion) const override;
+    bool CreateMuSig2AggregateSig(const std::vector<CPubKey>& participants, std::vector<uint8_t>& sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const override;
+    bool CreateMuSig2PartialSig(const SigningProvider& provider, uint256& partial_sig, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const std::vector<std::pair<uint256, bool>>& tweaks, SigVersion sigversion, const SignatureData& sigdata) const override;
+    std::vector<uint8_t> CreateMuSig2Nonce(const SigningProvider& provider, const CPubKey& aggregate_pubkey, const CPubKey& script_pubkey, const CPubKey& part_pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion, const SignatureData& sigdata) const override;
 };
 
 /** A signature checker that accepts all signatures */
@@ -88,6 +97,12 @@ struct SignatureData {
     std::map<std::vector<uint8_t>, std::vector<uint8_t>> hash256_preimages; ///< Mapping from a HASH256 hash to its preimage provided to solve a Script
     std::map<std::vector<uint8_t>, std::vector<uint8_t>> ripemd160_preimages; ///< Mapping from a RIPEMD160 hash to its preimage provided to solve a Script
     std::map<std::vector<uint8_t>, std::vector<uint8_t>> hash160_preimages; ///< Mapping from a HASH160 hash to its preimage provided to solve a Script
+    //! Map MuSig2 aggregate pubkeys to its participants
+    std::map<CPubKey, std::vector<CPubKey>> musig2_pubkeys;
+    //! Mapping from pair of MuSig2 aggregate pubkey, and tapleaf hash to map of MuSig2 participant pubkeys to MuSig2 public nonce
+    std::map<std::pair<CPubKey, uint256>, std::map<CPubKey, std::vector<uint8_t>>> musig2_pubnonces;
+    //! Mapping from pair of MuSig2 aggregate pubkey, and tapleaf hash to map of MuSig2 participant pubkeys to MuSig2 partial signature
+    std::map<std::pair<CPubKey, uint256>, std::map<CPubKey, uint256>> musig2_partial_sigs;
 
     SignatureData() = default;
     explicit SignatureData(const CScript& script) : scriptSig(script) {}

src/script/signingprovider.cpp

@@ -52,6 +52,31 @@ bool HidingSigningProvider::GetTaprootBuilder(const XOnlyPubKey& output_key, Tap
 {
     return m_provider->GetTaprootBuilder(output_key, builder);
 }
+std::vector<CPubKey> HidingSigningProvider::GetAggregateParticipantPubkeys(const CPubKey& pubkey) const
+{
+    if (m_hide_origin) return {};
+    return m_provider->GetAggregateParticipantPubkeys(pubkey);
+}
+
+std::map<CPubKey, std::vector<CPubKey>> HidingSigningProvider::GetAllAggregateParticipantPubkeys() const
+{
+    return m_provider->GetAllAggregateParticipantPubkeys();
+}
+
+void HidingSigningProvider::SetMuSig2SecNonce(const uint256& id, MuSig2SecNonce&& nonce) const
+{
+    m_provider->SetMuSig2SecNonce(id, std::move(nonce));
+}
+
+std::optional<std::reference_wrapper<MuSig2SecNonce>> HidingSigningProvider::GetMuSig2SecNonce(const uint256& session_id) const
+{
+    return m_provider->GetMuSig2SecNonce(session_id);
+}
+
+void HidingSigningProvider::DeleteMuSig2Session(const uint256& session_id) const
+{
+    m_provider->DeleteMuSig2Session(session_id);
+}
 
 bool FlatSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const { return LookupHelper(scripts, scriptid, script); }
 bool FlatSigningProvider::GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const { return LookupHelper(pubkeys, keyid, pubkey); }
@@ -82,6 +107,36 @@ bool FlatSigningProvider::GetTaprootBuilder(const XOnlyPubKey& output_key, Tapro
     return LookupHelper(tr_trees, output_key, builder);
 }
 
+std::vector<CPubKey> FlatSigningProvider::GetAggregateParticipantPubkeys(const CPubKey& pubkey) const
+{
+    const auto& it = aggregate_pubkeys.find(pubkey);
+    if (it == aggregate_pubkeys.end()) return {};
+    return it->second;
+}
+
+std::map<CPubKey, std::vector<CPubKey>> FlatSigningProvider::GetAllAggregateParticipantPubkeys() const
+{
+    return aggregate_pubkeys;
+}
+
+void FlatSigningProvider::SetMuSig2SecNonce(const uint256& session_id, MuSig2SecNonce&& nonce) const
+{
+    if (!musig2_secnonces) return;
+    musig2_secnonces->emplace(session_id, std::move(nonce));
+}
+
+std::optional<std::reference_wrapper<MuSig2SecNonce>> FlatSigningProvider::GetMuSig2SecNonce(const uint256& session_id) const
+{
+    const auto& it = musig2_secnonces->find(session_id);
+    if (it == musig2_secnonces->end()) return std::nullopt;
+    return it->second;
+}
+
+void FlatSigningProvider::DeleteMuSig2Session(const uint256& session_id) const
+{
+    musig2_secnonces->erase(session_id);
+}
+
 FlatSigningProvider& FlatSigningProvider::Merge(FlatSigningProvider&& b)
 {
     scripts.merge(b.scripts);
@@ -89,6 +144,8 @@ FlatSigningProvider& FlatSigningProvider::Merge(FlatSigningProvider&& b)
     keys.merge(b.keys);
     origins.merge(b.origins);
     tr_trees.merge(b.tr_trees);
+    aggregate_pubkeys.merge(b.aggregate_pubkeys);
+    if (!musig2_secnonces) musig2_secnonces = b.musig2_secnonces;
     return *this;
 }
 

src/script/signingprovider.h

@@ -9,11 +9,15 @@
 #include <addresstype.h>
 #include <attributes.h>
 #include <key.h>
+#include <musig.h>
 #include <pubkey.h>
 #include <script/keyorigin.h>
 #include <script/script.h>
 #include <sync.h>
 
+#include <functional>
+#include <optional>
+
 struct ShortestVectorFirstComparator
 {
     bool operator()(const std::vector<unsigned char>& a, const std::vector<unsigned char>& b) const
@@ -161,6 +165,11 @@ public:
     virtual bool GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const { return false; }
     virtual bool GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const { return false; }
     virtual bool GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const { return false; }
+    virtual std::vector<CPubKey> GetAggregateParticipantPubkeys(const CPubKey& pubkey) const { return {}; }
+    virtual std::map<CPubKey, std::vector<CPubKey>> GetAllAggregateParticipantPubkeys() const {return {}; }
+    virtual void SetMuSig2SecNonce(const uint256& id, MuSig2SecNonce&& nonce) const {}
+    virtual std::optional<std::reference_wrapper<MuSig2SecNonce>> GetMuSig2SecNonce(const uint256& session_id) const { return std::nullopt; }
+    virtual void DeleteMuSig2Session(const uint256& session_id) const {}
 
     bool GetKeyByXOnly(const XOnlyPubKey& pubkey, CKey& key) const
     {
@@ -204,6 +213,11 @@ public:
     bool GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const override;
     bool GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const override;
     bool GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const override;
+    std::vector<CPubKey> GetAggregateParticipantPubkeys(const CPubKey& pubkey) const override;
+    std::map<CPubKey, std::vector<CPubKey>> GetAllAggregateParticipantPubkeys() const override;
+    void SetMuSig2SecNonce(const uint256& id, MuSig2SecNonce&& nonce) const override;
+    std::optional<std::reference_wrapper<MuSig2SecNonce>> GetMuSig2SecNonce(const uint256& session_id) const override;
+    void DeleteMuSig2Session(const uint256& session_id) const override;
 };
 
 struct FlatSigningProvider final : public SigningProvider
@@ -213,6 +227,8 @@ struct FlatSigningProvider final : public SigningProvider
     std::map<CKeyID, std::pair<CPubKey, KeyOriginInfo>> origins;
     std::map<CKeyID, CKey> keys;
     std::map<XOnlyPubKey, TaprootBuilder> tr_trees; /** Map from output key to Taproot tree (which can then make the TaprootSpendData */
+    std::map<CPubKey, std::vector<CPubKey>> aggregate_pubkeys; /** MuSig2 aggregate pubkeys */
+    std::map<uint256, MuSig2SecNonce>* musig2_secnonces{nullptr};
 
     bool GetCScript(const CScriptID& scriptid, CScript& script) const override;
     bool GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const override;
@@ -221,6 +237,11 @@ struct FlatSigningProvider final : public SigningProvider
     bool GetKey(const CKeyID& keyid, CKey& key) const override;
     bool GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const override;
     bool GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const override;
+    std::vector<CPubKey> GetAggregateParticipantPubkeys(const CPubKey& pubkey) const override;
+    std::map<CPubKey, std::vector<CPubKey>> GetAllAggregateParticipantPubkeys() const override;
+    void SetMuSig2SecNonce(const uint256& id, MuSig2SecNonce&& nonce) const override;
+    std::optional<std::reference_wrapper<MuSig2SecNonce>> GetMuSig2SecNonce(const uint256& session_id) const override;
+    void DeleteMuSig2Session(const uint256& session_id) const override;
 
     FlatSigningProvider& Merge(FlatSigningProvider&& b) LIFETIMEBOUND;
 };

src/test/descriptor_tests.cpp

@@ -40,15 +40,17 @@ void CheckInferRaw(const CScript& script)
 }
 
 constexpr int DEFAULT = 0;
-constexpr int RANGE = 1; // Expected to be ranged descriptor
+constexpr int RANGE = 1 << 0; // Expected to be ranged descriptor
-constexpr int HARDENED = 2; // Derivation needs access to private keys
+constexpr int HARDENED = 1 << 1; // Derivation needs access to private keys
-constexpr int UNSOLVABLE = 4; // This descriptor is not expected to be solvable
+constexpr int UNSOLVABLE = 1 << 2; // This descriptor is not expected to be solvable
-constexpr int SIGNABLE = 8; // We can sign with this descriptor (this is not true when actual BIP32 derivation is used, as that's not integrated in our signing code)
+constexpr int SIGNABLE = 1 << 3; // We can sign with this descriptor (this is not true when actual BIP32 derivation is used, as that's not integrated in our signing code)
-constexpr int DERIVE_HARDENED = 16; // The final derivation is hardened, i.e. ends with *' or *h
+constexpr int DERIVE_HARDENED = 1 << 4; // The final derivation is hardened, i.e. ends with *' or *h
-constexpr int MIXED_PUBKEYS = 32;
+constexpr int MIXED_PUBKEYS = 1 << 5;
-constexpr int XONLY_KEYS = 64; // X-only pubkeys are in use (and thus inferring/caching may swap parity of pubkeys/keyids)
+constexpr int XONLY_KEYS = 1 << 6; // X-only pubkeys are in use (and thus inferring/caching may swap parity of pubkeys/keyids)
-constexpr int MISSING_PRIVKEYS = 128; // Not all private keys are available, so ToPrivateString will fail.
+constexpr int MISSING_PRIVKEYS = 1 << 7; // Not all private keys are available, so ToPrivateString will fail.
-constexpr int SIGNABLE_FAILS = 256; // We can sign with this descriptor, but actually trying to sign will fail
+constexpr int SIGNABLE_FAILS = 1 << 8; // We can sign with this descriptor, but actually trying to sign will fail
+constexpr int MUSIG = 1 << 9; // This is a MuSig so key counts will have an extra key
+constexpr int MUSIG_DERIVATION = 1 << 10; // MuSig with derivation from the aggregate key
 
 /** Compare two descriptors. If only one of them has a checksum, the checksum is ignored. */
 bool EqualDescriptor(std::string a, std::string b)
@@ -121,8 +123,18 @@ std::set<CPubKey> GetKeyData(const FlatSigningProvider& provider, int flags) {
 }
 
 std::set<std::pair<CPubKey, KeyOriginInfo>> GetKeyOriginData(const FlatSigningProvider& provider, int flags) {
+    std::set<CKeyID> ignored;
+    if (flags & MUSIG) {
+        for (const auto& [_, part_pks] : provider.aggregate_pubkeys) {
+            for (const auto& pk : part_pks) {
+                ignored.insert(pk.GetID());
+            }
+        }
+    }
+
     std::set<std::pair<CPubKey, KeyOriginInfo>> ret;
-    for (const auto& [_, data] : provider.origins) {
+    for (const auto& [keyid, data] : provider.origins) {
+        if (ignored.contains(keyid)) continue;
         if (flags & XONLY_KEYS) {
             unsigned char bytes[33];
             BOOST_CHECK_EQUAL(data.first.size(), 33);
@@ -283,7 +295,10 @@ void DoCheck(std::string prv, std::string pub, const std::string& norm_pub, int
             // Check whether keys are in the cache
             const auto& der_xpub_cache = desc_cache.GetCachedDerivedExtPubKeys();
             const auto& parent_xpub_cache = desc_cache.GetCachedParentExtPubKeys();
-            const size_t num_xpubs = CountXpubs(pub1);
+            size_t num_xpubs = CountXpubs(pub1);
+            if (flags & MUSIG_DERIVATION) {
+                num_xpubs++;
+            }
             if ((flags & RANGE) && !(flags & (DERIVE_HARDENED))) {
                 // For ranged, unhardened derivation, None of the keys in origins should appear in the cache but the cache should have parent keys
                 // But we can derive one level from each of those parent keys and find them all
@@ -301,16 +316,22 @@ void DoCheck(std::string prv, std::string pub, const std::string& norm_pub, int
                     const CPubKey& pk = origin_pair.second.first;
                     count_pks += pubkeys.count(pk);
                 }
+                if (flags & MUSIG_DERIVATION) {
+                    BOOST_CHECK_EQUAL(count_pks, 1);
+                    BOOST_CHECK_EQUAL(num_xpubs, pubkeys.size());
+                } else {
+                    if (flags & MUSIG) count_pks++; // One extra key for the aggregate key that is not in the cache
                     if (flags & MIXED_PUBKEYS) {
                         BOOST_CHECK_EQUAL(num_xpubs, count_pks);
                     } else {
                         BOOST_CHECK_EQUAL(script_provider_cached.origins.size(), count_pks);
                     }
+                }
             } else if (num_xpubs > 0) {
                 // For ranged, hardened derivation, or not ranged, but has an xpub, all of the keys should appear in the cache
-                BOOST_CHECK(der_xpub_cache.size() + parent_xpub_cache.size() == num_xpubs);
+                BOOST_CHECK_EQUAL(der_xpub_cache.size() + parent_xpub_cache.size(), num_xpubs);
                 if (!(flags & MIXED_PUBKEYS)) {
-                    BOOST_CHECK(num_xpubs == script_provider_cached.origins.size());
+                    BOOST_CHECK_EQUAL(script_provider_cached.origins.size(), num_xpubs);
                 }
                 // Get all of the derived pubkeys
                 std::set<CPubKey> pubkeys;
@@ -333,11 +354,18 @@ void DoCheck(std::string prv, std::string pub, const std::string& norm_pub, int
                     const CPubKey& pk = origin_pair.second.first;
                     count_pks += pubkeys.count(pk);
                 }
+                if (flags & MUSIG_DERIVATION && !(flags & MIXED_PUBKEYS)) {
+                    // pubkeys is one key per xpub + one derived key per xpub
+                    BOOST_CHECK_EQUAL(2 * count_pks, pubkeys.size());
+                    BOOST_CHECK_EQUAL(2 * num_xpubs, pubkeys.size());
+                } else {
+                    if (flags & MUSIG) count_pks++; // One extra key for the aggregate key that is not in the cache
                     if (flags & MIXED_PUBKEYS) {
                         BOOST_CHECK_EQUAL(num_xpubs, count_pks);
                     } else {
                         BOOST_CHECK_EQUAL(script_provider_cached.origins.size(), count_pks);
                     }
+                }
             } else if (!(flags & MIXED_PUBKEYS)) {
                 // Only const pubkeys, nothing should be cached
                 BOOST_CHECK(der_xpub_cache.empty());
@@ -1071,6 +1099,96 @@ BOOST_AUTO_TEST_CASE(descriptor_test)
     CheckInferDescriptor("76a914a31725c74421fadc50d35520ab8751ed120af80588ac", "pkh(04c56fe4a92d401bcbf1b3dfbe4ac3dac5602ca155a3681497f02c1b9a733b92d704e2da6ec4162e4846af9236ef4171069ac8b7f8234a8405b6cadd96f34f5a31)", {}, {{"04c56fe4a92d401bcbf1b3dfbe4ac3dac5602ca155a3681497f02c1b9a733b92d704e2da6ec4162e4846af9236ef4171069ac8b7f8234a8405b6cadd96f34f5a31", ""}});
     // Infer pk() from p2pk with uncompressed key
     CheckInferDescriptor("4104032540df1d3c7070a8ab3a9cdd304dfc7fd1e6541369c53c4c3310b2537d91059afc8b8e7673eb812a32978dabb78c40f2e423f7757dca61d11838c7aeeb5220ac", "pk(04032540df1d3c7070a8ab3a9cdd304dfc7fd1e6541369c53c4c3310b2537d91059afc8b8e7673eb812a32978dabb78c40f2e423f7757dca61d11838c7aeeb5220)", {}, {{"04032540df1d3c7070a8ab3a9cdd304dfc7fd1e6541369c53c4c3310b2537d91059afc8b8e7673eb812a32978dabb78c40f2e423f7757dca61d11838c7aeeb5220", ""}});
+
+    // MuSig2 parsing
+    Check("rawtr(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "rawtr(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "rawtr(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", XONLY_KEYS | MUSIG, {{"5120789d937bade6673538f3e28d8368dda4d0512f94da44cf477a505716d26a1575"}}, OutputType::BECH32M);
+    Check("tr(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "tr(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "tr(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", XONLY_KEYS | MUSIG, {{"512079e6c3e628c9bfbce91de6b7fb28e2aec7713d377cf260ab599dcbc40e542312"}}, OutputType::BECH32M);
+    Check("rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*))","rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*))","rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*))", XONLY_KEYS | RANGE | MUSIG, {{"5120754ccfd18ed4051de3b1144b6145cad4b2999387338dfb85ec392f2963ceaa3a"}, {"5120be80016576d2691ccc4077bc91d7ece4db34667d6e84829d5e08480cd4bc0b78"}, {"5120b7139e2f8b92570ad96c40c3b5e6557a5194e288a96df6f29980523365239d58"}}, OutputType::BECH32M, /*op_desc_id=*/std::nullopt, {{}, {0, 0}, {0, 1}, {0, 2}});
+    Check("rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*)","rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*)","rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*)", XONLY_KEYS | RANGE | MUSIG | MUSIG_DERIVATION, {{"51209508c08832f3bb9d5e8baf8cb5cfa3669902e2f2da19acea63ff47b93faa9bfc"}, {"51205ca1102663025a83dd9b5dbc214762c5a6309af00d48167d2d6483808525a298"}, {"51207dbed1b89c338df6a1ae137f133a19cae6e03d481196ee6f1a5c7d1aeb56b166"}}, OutputType::BECH32M, /*op_desc_id=*/std::nullopt, {{}, {0, 0}, {0, 1}, {0, 2}});
+    Check("rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/0,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/1)","rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/0,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/1)","rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/0,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/1)", XONLY_KEYS | MUSIG | MUSIG_DERIVATION, {{"51200e355f2bc9e754268e12bbd337499c2f7ffafc3101c41792709007b25a862532"}}, OutputType::BECH32M, /*op_desc_id=*/std::nullopt, {{}, {0}, {1}});
+    Check("tr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*,pk(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S))","tr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*,pk(f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9))","tr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*,pk(f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9))", XONLY_KEYS | RANGE | MUSIG | MUSIG_DERIVATION, {{"51201d377b637b5c73f670f5c8a96a2c0bb0d1a682a1fca6aba91fe673501a189782"}, {"51208950c83b117a6c208d5205ffefcf75b187b32512eb7f0d8577db8d9102833036"}, {"5120a49a477c61df73691b77fcd563a80a15ea67bb9c75470310ce5c0f25918db60d"}}, OutputType::BECH32M, /*op_desc_id=*/std::nullopt, {{}, {0, 0}, {0, 1}, {0, 2}});
+    Check("tr(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,pk(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*))","tr(f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,pk(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*))","tr(f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,pk(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*))", XONLY_KEYS | RANGE | MUSIG | MUSIG_DERIVATION, {{"512068983d461174afc90c26f3b2821d8a9ced9534586a756763b68371a404635cc8"}, {"5120368e2d864115181bdc8bb5dc8684be8d0760d5c33315570d71a21afce4afd43e"}, {"512097a1e6270b33ad85744677418bae5f59ea9136027223bc6e282c47c167b471d5"}}, OutputType::BECH32M, /*op_desc_id=*/std::nullopt, {{}, {0, 0}, {0, 1}, {0, 2}});
+    CheckMultipath("rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/<1;2;3>/0/*,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L/0/*,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4/0/0/<3;4;5>/*))",
+            "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/<1;2;3>/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/<3;4;5>/*))",
+            {
+                "rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/1/0/*,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L/0/*,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4/0/0/3/*))",
+                "rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/2/0/*,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L/0/*,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4/0/0/4/*))",
+                "rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/3/0/*,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L/0/*,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4/0/0/5/*))",
+            },
+            {
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/1/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/3/*))",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/2/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/4/*))",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/3/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/5/*))",
+            },
+            {
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/1/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/3/*))",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/2/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/4/*))",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/3/0/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/0/*,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t/0/0/5/*))",
+            },
+            XONLY_KEYS | RANGE | MUSIG,
+            {
+                {{"51204ba445a411bd8500476ef916e6d4dd7c137a77e0637e5b0e98339210d78d595a"},{"5120800394c4f39743734c9a15eaa171476814bed0ea19ad771037c5f1ceb20244a9"},{"512011658c4e00fae6f22b9adc2b3823ff3ec6367599783788f4aa8fe1ab3dd0a7ea"}},
+                {{"5120b977ae89f221762a61ee986fed7a493426462483afef46f7225765e015934961"},{"5120b70bf732ed38fcc2052075f83901f8588f1016f6741aaacce6e439a02235e5ed"},{"5120d7fa329159ae543b41ca81c7b0e916824ce5d13f61de5b6246dc55a3367f8596"}},
+                {{"5120cae8685560b38da78300cc06a230a0f47179f20689d71655a665bdd8c5c875cf"},{"5120ad51a056d67374c56c7f6d9bb1a6d0d5a20449f5805628334dbac8d4ed8686b5"},{"5120e080130242eae1fc92d8c84d7390697e80b4d1e54184bdcbccfc7d6c4fe9bb0f"}},
+            },
+            OutputType::BECH32M,
+            {
+                {{}, {1, 0, 0}, {1, 0, 1}, {1, 0, 2}, {0, 0}, {0, 1}, {0, 2}, {0, 0, 3, 0}, {0, 0, 3, 1}, {0, 0, 3, 2}},
+                {{}, {2, 0, 0}, {2, 0, 1}, {2, 0, 2}, {0, 0}, {0, 1}, {0, 2}, {0, 0, 4, 0}, {0, 0, 4, 1}, {0, 0, 4, 2}},
+                {{}, {3, 0, 0}, {3, 0, 1}, {3, 0, 2}, {0, 0}, {0, 1}, {0, 2}, {0, 0, 5, 0}, {0, 0, 5, 1}, {0, 0, 5, 2}},
+            }
+    );
+    CheckMultipath("rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4)/<3;4;5>/*)",
+            "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/<3;4;5>/*)",
+            {
+                "rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4)/3/*)",
+                "rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4)/4/*)",
+                "rawtr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L,xprv9s21ZrQH143K3jUwNHoqQNrtzJnJmx4Yup8NkNLdVQCymYbPbJXnPhwkfTfxZfptcs3rLAPUXS39oDLgrNKQGwbGsEmJJ8BU3RzQuvShEG4)/5/*)",
+            },
+            {
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/3/*)",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/4/*)",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/5/*)",
+            },
+            {
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/3/*)",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/4/*)",
+                "rawtr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y,xpub661MyMwAqRbcGDZQUKLqmWodYLcoBQnQH33yYkkF3jjxeLvY8qr2wWGEWkiKFaaQfJCoi3HeEq3Dc5DptfbCyjD38fNhSqtKc1UHaP4ba3t)/5/*)",
+            },
+            XONLY_KEYS | RANGE | MUSIG | MUSIG_DERIVATION,
+            {
+                {{"51204a0fecdd99c67eb2afca0efa9a008c8bbc4dbb5ccb094b3eee273127b1ababee"},{"512006120155e6bfd6a3abf8a697caaf5669058395ae0052283a1c6e852d373ceccd"},{"5120d46831206710fca12ef7b562a0812250fdda110146dc1b9ac3a099c81ebcef82"}},
+                {{"5120f2b491de0be3b53482253865a5e0f2d2dbdc425d59db0c48f01c6bed9c6687c2"},{"5120601daf543e702b9c28a02f33961dfddfad666d9218b3b0b80177420b37619683"},{"512081dc64aac07811399defde8c959e3a66c56b621360e55ff01c2d43dfe7928b66"}},
+                {{"51201bde67648efbd371e63fc5d30325113d0ad5fb853afc53e9b78302708d5fd865"},{"51205bf89fde498522610b5db4eb306b3e1499057aac6d9a56dea832adca4722858b"},{"5120b4a81ca1cc45973422d26d687ab3b586d18508a6dbbbcd38e841400c214c4e83"}},
+            },
+            OutputType::BECH32M,
+            {
+                {{}, {3, 0}, {3, 1}, {3, 2}},
+                {{}, {4, 0}, {4, 1}, {4, 2}},
+                {{}, {5, 0}, {5, 1}, {5, 2}},
+            }
+    );
+
+    // MuSig2 Parsing Failures
+    CheckUnparsable("pk(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "pk(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "pk(): musig() is only allowed in tr()");
+    CheckUnparsable("pkh(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "pkh(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "pkh(): musig() is only allowed in tr()");
+    CheckUnparsable("wpkh(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "wpkh(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "wpkh(): musig() is only allowed in tr()");
+    CheckUnparsable("combo(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "combo(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "combo(): musig() is only allowed in tr()");
+    CheckUnparsable("sh(wpkh(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66)))", "sh(wpkh(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66)))", "wpkh(): musig() is only allowed in tr()");
+    CheckUnparsable("sh(wsh(pk(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66)))", "sh(wsh(pk(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))))", "pk(): musig() is only allowed in tr()");
+    CheckUnparsable("wsh(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "wsh(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "A function is needed within P2WSH");
+    CheckUnparsable("sh(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "sh(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66))", "A function is needed within P2SH");
+    CheckUnparsable("tr(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66)/0/0)", "tr(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,023590a94e768f8e1815c2f24b4d80a8e3149316c3518ce7b7ad338368d038ca66)/0/0)", "tr(): musig(): Ranged musig() requires all participants to be xpubs");
+    CheckUnparsable("tr(musig(KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3qYjgd9M7rFU74sHUHy8S,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL)/0/0)", "tr(musig(02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9,03dff1d77f2a671c5f36183726db2341be58feae1da2deced843240f7b502ba659,xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL)/0/0)", "tr(): musig(): Ranged musig() requires all participants to be xpubs");
+    CheckUnparsable("tr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*)","tr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/*,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*)", "tr(): musig(): Cannot have ranged participant keys if musig() is also ranged");
+    CheckUnparsable("tr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0h/*)","tr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0h/*)", "tr(): musig(): cannot have hardened derivation steps");
+    CheckUnparsable("tr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*h)","tr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y)/0/*h)", "tr(): musig(): Cannot have hardened child derivation");
+    CheckUnparsable("tr(musig(xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc/<0;1>,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/<2;3>)/<3;4>)","tr(musig(xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/<0;1>,xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y/<2;3>)/<3;4>)", "tr(): musig(): Cannot have multipath participant keys if musig() is also multipath");
+    CheckUnparsable("tr(musig()/0)", "tr(musig()/0)", "tr(): musig(): Must contain key expressions");
+
+    // Fuzzer crash test cases
+    CheckUnparsable("pk(musig(dd}uue/00/)k(", "pk(musig(dd}uue/00/)k(", "Invalid musig() expression");
+    CheckUnparsable("tr(musig(tuus(oldepk(gg)ggggfgg)<,z(((((((((((((((((((((st)", "tr(musig(tuus(oldepk(gg)ggggfgg)<,z(((((((((((((((((((((st)","tr(): Too many ')' in musig() expression");
 }
 
 BOOST_AUTO_TEST_SUITE_END()

src/test/fuzz/key.cpp

@@ -279,7 +279,8 @@ FUZZ_TARGET(key, .init = initialize_key)
     {
         CPubKey child_pubkey;
         ChainCode child_chaincode;
-        const bool ok = pubkey.Derive(child_pubkey, child_chaincode, 0, random_uint256);
+        uint256 tweak;
+        const bool ok = pubkey.Derive(child_pubkey, child_chaincode, 0, random_uint256, tweak);
         assert(ok);
         assert(child_pubkey != pubkey);
         assert(child_pubkey.IsCompressed());

src/wallet/external_signer_scriptpubkeyman.cpp

@@ -79,7 +79,7 @@ util::Result<void> ExternalSignerScriptPubKeyMan::DisplayAddress(const CTxDestin
 }
 
 // If sign is true, transaction must previously have been filled
-std::optional<PSBTError> ExternalSignerScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
+std::optional<PSBTError> ExternalSignerScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
 {
     if (!sign) {
         return DescriptorScriptPubKeyMan::FillPSBT(psbt, txdata, sighash_type, false, bip32derivs, n_signed, finalize);

src/wallet/external_signer_scriptpubkeyman.h

@@ -35,7 +35,7 @@ class ExternalSignerScriptPubKeyMan : public DescriptorScriptPubKeyMan
   */
  util::Result<void> DisplayAddress(const CTxDestination& dest, const ExternalSigner& signer) const;
 
-  std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+  std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 };
 } // namespace wallet
 #endif // BITCOIN_WALLET_EXTERNAL_SIGNER_SCRIPTPUBKEYMAN_H

src/wallet/feebumper.cpp

@@ -343,8 +343,8 @@ bool SignTransaction(CWallet& wallet, CMutableTransaction& mtx) {
         // First fill transaction with our data without signing,
         // so external signers are not asked to sign more than once.
         bool complete;
-        wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, false /* sign */, true /* bip32derivs */);
+        wallet.FillPSBT(psbtx, complete, std::nullopt, false /* sign */, true /* bip32derivs */);
-        auto err{wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, true /* sign */, false  /* bip32derivs */)};
+        auto err{wallet.FillPSBT(psbtx, complete, std::nullopt, true /* sign */, false  /* bip32derivs */)};
         if (err) return false;
         complete = FinalizeAndExtractPSBT(psbtx, mtx);
         return complete;

src/wallet/interfaces.cpp

@@ -391,7 +391,7 @@ public:
         }
         return {};
     }
-    std::optional<PSBTError> fillPSBT(int sighash_type,
+    std::optional<PSBTError> fillPSBT(std::optional<int> sighash_type,
         bool sign,
         bool bip32derivs,
         size_t* n_signed,

src/wallet/rpc/backup.cpp

@@ -1091,6 +1091,9 @@ static UniValue ProcessImportDescriptor(ImportData& import_data, std::map<CKeyID
         std::tie(range_start, range_end) = ParseDescriptorRange(data["range"]);
     }
 
+    // Only single key descriptors are allowed to be imported to a legacy wallet's keypool
+    bool can_keypool = parsed_descs.at(0)->IsSingleKey();
+
     const UniValue& priv_keys = data.exists("keys") ? data["keys"].get_array() : UniValue();
 
     for (size_t j = 0; j < parsed_descs.size(); ++j) {
@@ -1107,9 +1110,11 @@ static UniValue ProcessImportDescriptor(ImportData& import_data, std::map<CKeyID
             std::vector<CScript> scripts_temp;
             parsed_desc->Expand(i, keys, scripts_temp, out_keys);
             std::copy(scripts_temp.begin(), scripts_temp.end(), std::inserter(script_pub_keys, script_pub_keys.end()));
+            if (can_keypool) {
                 for (const auto& key_pair : out_keys.pubkeys) {
                     ordered_pubkeys.emplace_back(key_pair.first, desc_internal);
                 }
+            }
 
             for (const auto& x : out_keys.scripts) {
                 import_data.import_scripts.emplace(x.second);

src/wallet/rpc/spend.cpp

@@ -100,8 +100,8 @@ static UniValue FinishTransaction(const std::shared_ptr<CWallet> pwallet, const
     // First fill transaction with our data without signing,
     // so external signers are not asked to sign more than once.
     bool complete;
-    pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/false, /*bip32derivs=*/true);
+    pwallet->FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/true);
-    const auto err{pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/true, /*bip32derivs=*/false)};
+    const auto err{pwallet->FillPSBT(psbtx, complete, std::nullopt, /*sign=*/true, /*bip32derivs=*/false)};
     if (err) {
         throw JSONRPCPSBTError(*err);
     }
@@ -951,12 +951,15 @@ RPCHelpMan signrawtransactionwithwallet()
     // Parse the prevtxs array
     ParsePrevouts(request.params[1], nullptr, coins);
 
-    int nHashType = ParseSighashString(request.params[2]);
+    std::optional<int> nHashType = ParseSighashString(request.params[2]);
+    if (!nHashType) {
+        nHashType = SIGHASH_DEFAULT;
+    }
 
     // Script verification errors
     std::map<int, bilingual_str> input_errors;
 
-    bool complete = pwallet->SignTransaction(mtx, coins, nHashType, input_errors);
+    bool complete = pwallet->SignTransaction(mtx, coins, *nHashType, input_errors);
     UniValue result(UniValue::VOBJ);
     SignTransactionResultToJSON(mtx, complete, coins, input_errors, result);
     return result;
@@ -1169,7 +1172,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
     } else {
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const auto err{pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/false, /*bip32derivs=*/true)};
+        const auto err{pwallet->FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/true)};
         CHECK_NONFATAL(!err);
         CHECK_NONFATAL(!complete);
         DataStream ssTx{};
@@ -1623,7 +1626,7 @@ RPCHelpMan walletprocesspsbt()
     }
 
     // Get the sighash type
-    int nHashType = ParseSighashString(request.params[2]);
+    std::optional<int> nHashType = ParseSighashString(request.params[2]);
 
     // Fill transaction with our data and also sign
     bool sign = request.params[1].isNull() ? true : request.params[1].get_bool();
@@ -1769,7 +1772,7 @@ RPCHelpMan walletcreatefundedpsbt()
     // Fill transaction with out data but don't sign
     bool bip32derivs = request.params[4].isNull() ? true : request.params[4].get_bool();
     bool complete = true;
-    const auto err{wallet.FillPSBT(psbtx, complete, 1, /*sign=*/false, /*bip32derivs=*/bip32derivs)};
+    const auto err{wallet.FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/bip32derivs)};
     if (err) {
         throw JSONRPCPSBTError(*err);
     }

src/wallet/scriptpubkeyman.cpp

@@ -638,7 +638,7 @@ SigningResult LegacyScriptPubKeyMan::SignMessage(const std::string& message, con
     return SigningResult::SIGNING_FAILED;
 }
 
-std::optional<PSBTError> LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
+std::optional<PSBTError> LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
 {
     if (n_signed) {
         *n_signed = 0;
@@ -651,11 +651,6 @@ std::optional<PSBTError> LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransact
             continue;
         }
 
-        // Get the Sighash type
-        if (sign && input.sighash_type != std::nullopt && *input.sighash_type != sighash_type) {
-            return PSBTError::SIGHASH_MISMATCH;
-        }
-
         // Check non_witness_utxo has specified prevout
         if (input.non_witness_utxo) {
             if (txin.prevout.n >= input.non_witness_utxo->vout.size()) {
@@ -665,7 +660,10 @@ std::optional<PSBTError> LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransact
             // There's no UTXO so we can just skip this now
             continue;
         }
-        SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
+        PSBTError res = SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
+        if (res != PSBTError::OK && res != PSBTError::INCOMPLETE) {
+            return res;
+        }
 
         bool signed_one = PSBTInputSigned(input);
         if (n_signed && (signed_one || !sign)) {
@@ -2498,6 +2496,10 @@ std::unique_ptr<FlatSigningProvider> DescriptorScriptPubKeyMan::GetSigningProvid
         FlatSigningProvider master_provider;
         master_provider.keys = GetKeys();
         m_wallet_descriptor.descriptor->ExpandPrivate(index, master_provider, *out_keys);
+
+        // Always include musig_secnonces as this descriptor may have a participant private key
+        // but not a musig() descriptor
+        out_keys->musig2_secnonces = &m_musig2_secnonces;
     }
 
     return out_keys;
@@ -2545,7 +2547,7 @@ SigningResult DescriptorScriptPubKeyMan::SignMessage(const std::string& message,
     return SigningResult::OK;
 }
 
-std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
+std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
 {
     if (n_signed) {
         *n_signed = 0;
@@ -2558,11 +2560,6 @@ std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTran
             continue;
         }
 
-        // Get the Sighash type
-        if (sign && input.sighash_type != std::nullopt && *input.sighash_type != sighash_type) {
-            return PSBTError::SIGHASH_MISMATCH;
-        }
-
         // Get the scriptPubKey to know which SigningProvider to use
         CScript script;
         if (!input.witness_utxo.IsNull()) {
@@ -2620,7 +2617,10 @@ std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTran
             }
         }
 
-        SignPSBTInput(HidingSigningProvider(keys.get(), /*hide_secret=*/!sign, /*hide_origin=*/!bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
+        PSBTError res = SignPSBTInput(HidingSigningProvider(keys.get(), /*hide_secret=*/!sign, /*hide_origin=*/!bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
+        if (res != PSBTError::OK && res != PSBTError::INCOMPLETE) {
+            return res;
+        }
 
         bool signed_one = PSBTInputSigned(input);
         if (n_signed && (signed_one || !sign)) {

src/wallet/scriptpubkeyman.h

@@ -10,6 +10,7 @@
 #include <common/signmessage.h>
 #include <common/types.h>
 #include <logging.h>
+#include <musig.h>
 #include <node/types.h>
 #include <psbt.h>
 #include <script/descriptor.h>
@@ -246,7 +247,7 @@ public:
     /** Sign a message with the given script */
     virtual SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const { return SigningResult::SIGNING_FAILED; };
     /** Adds script and derivation path information to a PSBT, and optionally signs it. */
-    virtual std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return common::PSBTError::UNSUPPORTED; }
+    virtual std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = std::nullopt, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return common::PSBTError::UNSUPPORTED; }
 
     virtual uint256 GetID() const { return uint256(); }
 
@@ -492,7 +493,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+    std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = std::nullopt, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 
@@ -605,6 +606,20 @@ private:
     //! Number of pre-generated keys/scripts (part of the look-ahead process, used to detect payments)
     int64_t m_keypool_size GUARDED_BY(cs_desc_man){DEFAULT_KEYPOOL_SIZE};
 
+    /** Map of a session id to MuSig2 secnonce
+     *
+     * Stores MuSig2 secnonces while the MuSig2 signing session is still ongoing.
+     * Note that these secnonces must not be reused. In order to avoid being tricked into
+     * reusing a nonce, this map is held only in memory and must not be written to disk.
+     * The side effect is that signing sessions cannot persist across restarts, but this
+     * must be done in order to prevent nonce reuse.
+     *
+     * The session id is an arbitrary value set by the signer in order for the signing logic
+     * to find ongoing signing sessions. It is the SHA256 of aggregate xonly key, + participant pubkey + sighash.
+     */
+    // TODO: Check thread safety of this
+    mutable std::map<uint256, MuSig2SecNonce> m_musig2_secnonces;
+
     bool AddDescriptorKeyWithDB(WalletBatch& batch, const CKey& key, const CPubKey &pubkey) EXCLUSIVE_LOCKS_REQUIRED(cs_desc_man);
 
     KeyMap GetKeys() const EXCLUSIVE_LOCKS_REQUIRED(cs_desc_man);
@@ -681,7 +696,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+    std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = std::nullopt, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 

src/wallet/test/fuzz/scriptpubkeyman.cpp

@@ -188,7 +188,8 @@ FUZZ_TARGET(scriptpubkeyman, .init = initialize_spkm)
                 }
                 auto psbt{*opt_psbt};
                 const PrecomputedTransactionData txdata{PrecomputePSBTData(psbt)};
-                const int sighash_type{fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 150)};
+                std::optional<int> sighash_type{fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 151)};
+                if (sighash_type == 151) sighash_type = std::nullopt;
                 auto sign  = fuzzed_data_provider.ConsumeBool();
                 auto bip32derivs = fuzzed_data_provider.ConsumeBool();
                 auto finalize = fuzzed_data_provider.ConsumeBool();

src/wallet/test/psbt_wallet_tests.cpp

@@ -64,7 +64,7 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
 
     // Fill transaction with our data
     bool complete = true;
-    BOOST_REQUIRE(!m_wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, false, true));
+    BOOST_REQUIRE(!m_wallet.FillPSBT(psbtx, complete, std::nullopt, false, true));
 
     // Get the final tx
     DataStream ssTx{};
@@ -77,7 +77,7 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
 
     // Try to sign the mutated input
     SignatureData sigdata;
-    BOOST_CHECK(m_wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, true, true));
+    BOOST_CHECK(m_wallet.FillPSBT(psbtx, complete, std::nullopt, true, true));
 }
 
 BOOST_AUTO_TEST_CASE(parse_hd_keypath)

src/wallet/test/walletload_tests.cpp

@@ -26,6 +26,7 @@ public:
     bool IsRange() const override { return false; }
     bool IsSolvable() const override { return false; }
     bool IsSingleType() const override { return true; }
+    bool IsSingleKey() const override { return true; }
     bool ToPrivateString(const SigningProvider& provider, std::string& out) const override { return false; }
     bool ToNormalizedString(const SigningProvider& provider, std::string& out, const DescriptorCache* cache = nullptr) const override { return false; }
     bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const override { return false; };

src/wallet/wallet.cpp

@@ -2197,7 +2197,7 @@ bool CWallet::SignTransaction(CMutableTransaction& tx, const std::map<COutPoint,
     return false;
 }
 
-std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& complete, int sighash_type, bool sign, bool bip32derivs, size_t * n_signed, bool finalize) const
+std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& complete, std::optional<int> sighash_type, bool sign, bool bip32derivs, size_t * n_signed, bool finalize) const
 {
     if (n_signed) {
         *n_signed = 0;
@@ -2240,7 +2240,7 @@ std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bo
         }
     }
 
-    RemoveUnnecessaryTransactions(psbtx, sighash_type);
+    RemoveUnnecessaryTransactions(psbtx);
 
     // Complete if every input is now signed
     complete = true;

src/wallet/wallet.h

@@ -663,7 +663,7 @@ public:
      */
     std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbtx,
                   bool& complete,
-                  int sighash_type = SIGHASH_DEFAULT,
+                  std::optional<int> sighash_type = std::nullopt,
                   bool sign = true,
                   bool bip32derivs = true,
                   size_t* n_signed = nullptr,

test/functional/rpc_psbt.py

@@ -27,13 +27,14 @@ from test_framework.psbt import (
     PSBT_GLOBAL_UNSIGNED_TX,
     PSBT_IN_RIPEMD160,
     PSBT_IN_SHA256,
+    PSBT_IN_SIGHASH_TYPE,
     PSBT_IN_HASH160,
     PSBT_IN_HASH256,
     PSBT_IN_NON_WITNESS_UTXO,
     PSBT_IN_WITNESS_UTXO,
     PSBT_OUT_TAP_TREE,
 )
-from test_framework.script import CScript, OP_TRUE
+from test_framework.script import CScript, OP_TRUE, SIGHASH_ALL, SIGHASH_ANYONECANPAY
 from test_framework.script_util import MIN_STANDARD_TX_NONWITNESS_SIZE
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -201,6 +202,100 @@ class PSBTTest(BitcoinTestFramework):
 
         wallet.unloadwallet()
 
+    def test_sighash_mismatch(self):
+        self.log.info("Test sighash type mismatches")
+        self.nodes[0].createwallet("sighash_mismatch")
+        wallet = self.nodes[0].get_wallet_rpc("sighash_mismatch")
+        def_wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+
+        addr = wallet.getnewaddress(address_type="bech32")
+        def_wallet.sendtoaddress(addr, 5)
+        self.generate(self.nodes[0], 6)
+
+        # Retrieve the descriptors so we can do all of the tests with descriptorprocesspsbt as well
+        if self.options.descriptors:
+            descs = wallet.listdescriptors(True)["descriptors"]
+        else:
+            descs = [descsum_create(f"wpkh({wallet.dumpprivkey(addr)})")]
+
+        # Make a PSBT
+        psbt = wallet.walletcreatefundedpsbt([], [{def_wallet.getnewaddress(): 1}])["psbt"]
+
+        # Modify the PSBT and insert a sighash field for ALL|ANYONECANPAY on input 0
+        mod_psbt = PSBT.from_base64(psbt)
+        mod_psbt.i[0].map[PSBT_IN_SIGHASH_TYPE] = (SIGHASH_ALL | SIGHASH_ANYONECANPAY).to_bytes(4, byteorder="little")
+        psbt = mod_psbt.to_base64()
+
+        # Mismatching sighash type fails
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True, "DEFAULT")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True, "ALL")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True, "NONE")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True, "SINGLE")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True, "NONE|ANYONECANPAY")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True, "SINGLE|ANYONECANPAY")
+
+        # No sighash type specified fails
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", wallet.walletprocesspsbt, psbt, True)
+
+        # Matching sighash type succeeds
+        proc = wallet.walletprocesspsbt(psbt, True, "ALL|ANYONECANPAY")
+        assert_equal(proc["complete"], True)
+
+        # Repeat with descriptorprocesspsbt
+        # Mismatching sighash type fails
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs, "DEFAULT")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs, "ALL")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs, "NONE")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs, "SINGLE")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs, "NONE|ANYONECANPAY")
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs, "SINGLE|ANYONECANPAY")
+
+        # No sighash type specified fails
+        assert_raises_rpc_error(-22, "Specified sighash value does not match value stored in PSBT", self.nodes[0].descriptorprocesspsbt, psbt, descs)
+
+        # Matching sighash type succeeds
+        proc = self.nodes[0].descriptorprocesspsbt(psbt, descs, "ALL|ANYONECANPAY")
+        assert_equal(proc["complete"], True)
+
+        wallet.unloadwallet()
+
+    def test_sighash_adding(self):
+        self.log.info("Test adding of sighash type field")
+        self.nodes[0].createwallet("sighash_adding")
+        wallet = self.nodes[0].get_wallet_rpc("sighash_adding")
+        def_wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+
+        addr = wallet.getnewaddress(address_type="bech32")
+        def_wallet.sendtoaddress(addr, 5)
+        self.generate(self.nodes[0], 6)
+
+        # Make a PSBT
+        psbt = wallet.walletcreatefundedpsbt([], [{def_wallet.getnewaddress(): 1}])["psbt"]
+        psbt = wallet.walletprocesspsbt(psbt=psbt, sighashtype="ALL|ANYONECANPAY", finalize=False)["psbt"]
+
+        # Check that the PSBT has a sighash field on all inputs
+        dec_psbt = self.nodes[0].decodepsbt(psbt)
+        for input in dec_psbt["inputs"]:
+            assert_equal(input["sighash"], "ALL|ANYONECANPAY")
+
+        # Make sure we can still finalize the transaction
+        fin_res = self.nodes[0].finalizepsbt(psbt)
+        assert_equal(fin_res["complete"], True)
+        fin_hex = fin_res["hex"]
+
+        # Change the sighash field to a different value and make sure we still finalize to the same thing
+        mod_psbt = PSBT.from_base64(psbt)
+        mod_psbt.i[0].map[PSBT_IN_SIGHASH_TYPE] = (SIGHASH_ALL).to_bytes(4, byteorder="little")
+        psbt = mod_psbt.to_base64()
+        fin_res = self.nodes[0].finalizepsbt(psbt)
+        assert_equal(fin_res["complete"], True)
+        assert_equal(fin_res["hex"], fin_hex)
+
+        self.nodes[0].sendrawtransaction(fin_res["hex"])
+        self.generate(self.nodes[0], 1)
+
+        wallet.unloadwallet()
+
     def assert_change_type(self, psbtx, expected_type):
         """Assert that the given PSBT has a change output with the given type."""
 
@@ -1051,6 +1146,8 @@ class PSBTTest(BitcoinTestFramework):
         self.log.info("Test descriptorprocesspsbt raises if an invalid sighashtype is passed")
         assert_raises_rpc_error(-8, "'all' is not a valid sighash parameter.", self.nodes[2].descriptorprocesspsbt, psbt, [descriptor], sighashtype="all")
 
+        self.test_sighash_mismatch()
+        self.test_sighash_adding()
 
 if __name__ == '__main__':
     PSBTTest(__file__).main()

test/functional/test_runner.py

@@ -392,6 +392,7 @@ BASE_SCRIPTS = [
     'mempool_datacarrier.py',
     'feature_coinstatsindex.py',
     'wallet_orphanedreward.py',
+    'wallet_musig.py --descriptors',
     'wallet_timelock.py',
     'p2p_permissions.py',
     'feature_blocksdir.py',

test/functional/wallet_musig.py

@@ -0,0 +1,194 @@
+#!/usr/bin/env python3
+# Copyright (c) 2024 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+import re
+
+from test_framework.descriptors import descsum_create
+from test_framework.key import H_POINT
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+PRIVKEY_RE = re.compile(r"^tr\((.+?)/.+\)#.{8}$")
+PUBKEY_RE = re.compile(r"^tr\((\[.+?\].+?)/.+\)#.{8}$")
+ORIGIN_PATH_RE = re.compile(r"^\[\w{8}(/.*)\].*$")
+MULTIPATH_RE = re.compile(r"(.*?)<(\d+);(\d+)>")
+
+
+class WalletMuSigTest(BitcoinTestFramework):
+    WALLET_NUM = 0
+    def add_options(self, parser):
+        self.add_wallet_options(parser, legacy=False)
+
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_no_wallet()
+
+    def do_test(self, comment, pattern, sighash_type=None):
+        self.log.info(f"Testing {comment}")
+        def_wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+        has_int = "<" in pattern and ">" in pattern
+
+        wallets = []
+        keys = []
+
+        pat = pattern.replace("$H", H_POINT)
+
+        # Figure out how many wallets are needed and create them
+        exp_key_leaf = 0
+        for i in range(10):
+            if f"${i}" in pat:
+                exp_key_leaf += pat.count(f"${i}")
+                wallet_name = f"musig_{self.WALLET_NUM}"
+                self.WALLET_NUM += 1
+                self.nodes[0].createwallet(wallet_name)
+                wallet = self.nodes[0].get_wallet_rpc(wallet_name)
+                wallets.append(wallet)
+
+                for priv_desc in wallet.listdescriptors(True)["descriptors"]:
+                    desc = priv_desc["desc"]
+                    if not desc.startswith("tr("):
+                        continue
+                    privkey = PRIVKEY_RE.search(desc).group(1)
+                    break
+                for pub_desc in wallet.listdescriptors()["descriptors"]:
+                    desc = pub_desc["desc"]
+                    if not desc.startswith("tr("):
+                        continue
+                    pubkey = PUBKEY_RE.search(desc).group(1)
+                    # Since the pubkey is derived from the private key that we have, we need
+                    # to extract and insert the origin path from the pubkey as well.
+                    privkey += ORIGIN_PATH_RE.search(pubkey).group(1)
+                    break
+                keys.append((privkey, pubkey))
+
+        # Construct and import each wallet's musig descriptor
+        for i, wallet in enumerate(wallets):
+            desc = pat
+            import_descs = []
+            for j, (priv, pub) in enumerate(keys):
+                if j == i:
+                    desc = desc.replace(f"${i}", priv)
+                else:
+                    desc = desc.replace(f"${j}", pub)
+
+            import_descs.append({
+                "desc": descsum_create(desc),
+                "active": True,
+                "timestamp": "now",
+            })
+
+            res = wallet.importdescriptors(import_descs)
+            for r in res:
+                assert_equal(r["success"], True)
+
+        # Check that the wallets agree on the same musig address
+        addr = None
+        change_addr = None
+        for wallet in wallets:
+            if addr is None:
+                addr = wallet.getnewaddress(address_type="bech32m")
+            else:
+                assert_equal(addr, wallet.getnewaddress(address_type="bech32m"))
+            if has_int:
+                if change_addr is None:
+                    change_addr = wallet.getrawchangeaddress(address_type="bech32m")
+                else:
+                    assert_equal(change_addr, wallet.getrawchangeaddress(address_type="bech32m"))
+
+        # Fund that address
+        def_wallet.sendtoaddress(addr, 10)
+        self.generate(self.nodes[0], 1)
+
+        # Spend that UTXO
+        utxo = wallets[0].listunspent()[0]
+        psbt = wallets[0].send(outputs=[{def_wallet.getnewaddress(): 5}], inputs=[utxo], change_type="bech32m")["psbt"]
+
+        dec_psbt = self.nodes[0].decodepsbt(psbt)
+        assert_equal(len(dec_psbt["inputs"]), 1)
+        assert_equal(len(dec_psbt["inputs"][0]["musig2_participant_pubkeys"]), pattern.count("musig("))
+
+        # Retrieve all participant pubkeys
+        part_pks = set()
+        for agg in dec_psbt["inputs"][0]["musig2_participant_pubkeys"]:
+            for part_pub in agg["participant_pubkeys"]:
+                part_pks.add(part_pub[2:])
+        # Check that there are as many participants as we expected
+        assert_equal(len(part_pks), len(keys))
+        # Check that each participant has a derivation path
+        for deriv_path in dec_psbt["inputs"][0]["taproot_bip32_derivs"]:
+            if deriv_path["pubkey"] in part_pks:
+                part_pks.remove(deriv_path["pubkey"])
+        assert_equal(len(part_pks), 0)
+
+        # Add pubnonces
+        nonce_psbts = []
+        for wallet in wallets:
+            proc = wallet.walletprocesspsbt(psbt=psbt, sighashtype=sighash_type)
+            assert_equal(proc["complete"], False)
+            nonce_psbts.append(proc["psbt"])
+
+        comb_nonce_psbt = self.nodes[0].combinepsbt(nonce_psbts)
+
+        dec_psbt = self.nodes[0].decodepsbt(comb_nonce_psbt)
+        assert_equal(len(dec_psbt["inputs"][0]["musig2_pubnonces"]), exp_key_leaf)
+        for pn in dec_psbt["inputs"][0]["musig2_pubnonces"]:
+            pubkey = pn["aggregate_pubkey"][2:]
+            if pubkey in dec_psbt["inputs"][0]["witness_utxo"]["scriptPubKey"]["hex"]:
+                continue
+            elif "taproot_scripts" in dec_psbt["inputs"][0]:
+                for leaf_scripts in dec_psbt["inputs"][0]["taproot_scripts"]:
+                    if pubkey in leaf_scripts["script"]:
+                        break
+                else:
+                    assert False, "Aggregate pubkey for pubnonce not seen as output key, internal key, or in any scripts"
+            else:
+                assert False, "Aggregate pubkey for pubnonce not seen as output key or internal key"
+
+        # Add partial sigs
+        psig_psbts = []
+        for wallet in wallets:
+            proc = wallet.walletprocesspsbt(psbt=comb_nonce_psbt, sighashtype=sighash_type)
+            assert_equal(proc["complete"], False)
+            psig_psbts.append(proc["psbt"])
+
+        comb_psig_psbt = self.nodes[0].combinepsbt(psig_psbts)
+
+        dec_psbt = self.nodes[0].decodepsbt(comb_psig_psbt)
+        assert_equal(len(dec_psbt["inputs"][0]["musig2_partial_sigs"]), exp_key_leaf)
+        for ps in dec_psbt["inputs"][0]["musig2_partial_sigs"]:
+            pubkey = ps["aggregate_pubkey"][2:]
+            if pubkey in dec_psbt["inputs"][0]["witness_utxo"]["scriptPubKey"]["hex"]:
+                continue
+            elif "taproot_scripts" in dec_psbt["inputs"][0]:
+                for leaf_scripts in dec_psbt["inputs"][0]["taproot_scripts"]:
+                    if pubkey in leaf_scripts["script"]:
+                        break
+                else:
+                    assert False, "Aggregate pubkey for partial sig not seen as output key, internal key, or in any scripts"
+            else:
+                assert False, "Aggregate pubkey for partial sig not seen as output key or internal key"
+
+        # Non-participant aggregates partial sigs and send
+        finalized = self.nodes[0].finalizepsbt(comb_psig_psbt)
+        assert_equal(finalized["complete"], True)
+        assert "hex" in finalized
+        self.nodes[0].sendrawtransaction(finalized["hex"])
+
+    def run_test(self):
+        self.do_test("rawtr(musig(keys/*))", "rawtr(musig($0/<0;1>/*,$1/<1;2>/*,$2/<2;3>/*))")
+        self.do_test("rawtr(musig(keys/*)) with ALL|ANYONECANPAY", "rawtr(musig($0/<0;1>/*,$1/<1;2>/*,$2/<2;3>/*))", "ALL|ANYONECANPAY")
+        self.do_test("tr(musig(keys/*))", "tr(musig($0/<0;1>/*,$1/<1;2>/*,$2/<2;3>/*))")
+        self.do_test("rawtr(musig/*)", "rawtr(musig($0,$1,$2)/<0;1>/*)")
+        self.do_test("tr(musig/*)", "tr(musig($0,$1,$2)/<0;1>/*)")
+        self.do_test("tr(H, pk(musig(keys/*)))", "tr($H,pk(musig($0/<0;1>/*,$1/<1;2>/*,$2/<2;3>/*)))")
+        self.do_test("tr(H,pk(musig/*))", "tr($H,pk(musig($0,$1,$2)/<0;1>/*))")
+        self.do_test("tr(H,{pk(musig/*), pk(musig/*)})", "tr($H,{pk(musig($0,$1,$2)/<0;1>/*),pk(musig($3,$4,$5)/0/*)})")
+        self.do_test("tr(H,{pk(musig/*), pk(same keys different musig/*)})", "tr($H,{pk(musig($0,$1,$2)/<0;1>/*),pk(musig($1,$2)/0/*)})")
+
+
+if __name__ == '__main__':
+    WalletMuSigTest(__file__).main()