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Add secp256k1_ec_pubkey_compress(), with test similar to the related decompress() function.

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Thomas Kerin 2015-07-13 13:09:00 +01:00
parent 873a453d26
commit 99fd963bd5
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GPG key ID: 0883651DBDD5E4E5
3 changed files with 45 additions and 5 deletions
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21
include/secp256k1.h
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@ -260,10 +260,27 @@ SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
int compressed
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Compress a public key.
* In: ctx: pointer to a context object (cannot be NULL)
* pubkeyin: pointer to a 33-byte or 65-byte public key (cannot be NULL)
* Out: pubkeyout: pointer to a 33-byte array to put the compressed public key (cannot be NULL)
* May alias pubkeyin.
* pubkeylen: pointer to the size of the public key pointed to by pubkeyin (cannot be NULL)
* It will be updated to reflect the size of the public key in pubkeyout.
* Returns: 0: pubkeyin was invalid
* 1: pubkeyin was valid, and pubkeyout is its compressed version
*/
SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_compress(
const secp256k1_context_t* ctx,
const unsigned char *pubkeyin,
unsigned char *pubkeyout,
int *pubkeylen
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Decompress a public key.
* In: ctx: pointer to a context object (cannot be NULL)
* In: pubkeyin: pointer to a 33-byte or 65-byte public key (cannot be NULL)
* In/Out: pubkeyout: pointer to a 65-byte array to put the decompressed public key (cannot be NULL)
* pubkeyin: pointer to a 33-byte or 65-byte public key (cannot be NULL)
* Out: pubkeyout: pointer to a 65-byte array to put the decompressed public key (cannot be NULL)
* May alias pubkeyin.
* pubkeylen: pointer to the size of the public key pointed to by pubkeyin (cannot be NULL)
* It will be updated to reflect the size of the public key in pubkeyout.

15
src/secp256k1.c
View file

@ -285,6 +285,21 @@ int secp256k1_ec_pubkey_decompress(const secp256k1_context_t* ctx, const unsigne
return ret;
}
int secp256k1_ec_pubkey_compress(const secp256k1_context_t* ctx, const unsigned char *pubkeyin, unsigned char *pubkeyout, int *pubkeylen) {
secp256k1_ge_t p;
int ret = 0;
DEBUG_CHECK(pubkeyin != NULL);
DEBUG_CHECK(pubkeyout != NULL);
DEBUG_CHECK(pubkeylen != NULL);
(void)ctx;
if (secp256k1_eckey_pubkey_parse(&p, pubkeyin, *pubkeylen)) {
ret = secp256k1_eckey_pubkey_serialize(&p, pubkeyout, pubkeylen, 1);
}
return ret;
}
int secp256k1_ec_privkey_tweak_add(const secp256k1_context_t* ctx, unsigned char *seckey, const unsigned char *tweak) {
secp256k1_scalar_t term;
secp256k1_scalar_t sec;

14
src/tests.c
View file

@ -1512,14 +1512,22 @@ void test_ecdsa_end_to_end(void) {
CHECK(secp256k1_ec_pubkey_create(ctx, pubkey, &pubkeylen, privkey, (secp256k1_rand32() & 3) != 0) == 1);
if (secp256k1_rand32() & 1) {
unsigned char pubkey2[65] = {0};
int pubkey2len = pubkeylen;
unsigned char pubkey3RE[33] = {0};
int pubkey2len = pubkeylen, pubkey3len = pubkeylen;
/* Decompress into a new array */
CHECK(secp256k1_ec_pubkey_decompress(ctx, pubkey, pubkey2, &pubkey2len));
/* Compress into a new array */
CHECK(secp256k1_ec_pubkey_compress(ctx, pubkey, pubkey3RE, &pubkey3len));
/* Check that the key was changed iff it was originally compressed */
if (pubkeylen == 65) {
CHECK(memcmp(pubkey, pubkey2, 65) == 0);
CHECK(memcmp(pubkey, pubkey2, 65) == 0); /* Values should be the same */
CHECK(memcmp(pubkey3RE, pubkey, 33) != 0); /* Means it should have been compressed */
} else {
CHECK(memcmp(pubkey, pubkey2, 65) != 0);
CHECK(memcmp(pubkey, pubkey2, 65) != 0); /* Should have been decompressed */
CHECK(memcmp(pubkey3RE, pubkey, 33) == 0); /* Therefore compressed key should equal initial pubkey */
}
/* Decompress in place */
CHECK(secp256k1_ec_pubkey_decompress(ctx, pubkey, pubkey, &pubkeylen));