From 3bca6cd61a8cd677023f18c146f2a6534829b1c7 Mon Sep 17 00:00:00 2001 From: Sebastian Falbesoner Date: Wed, 19 Oct 2022 19:12:43 +0200 Subject: [PATCH] test: add compact block filter (BIP158) helper routines By now, we add one helper for calculating ranged hashes and another one for finding relevant scriptPubKeys given a block. --- test/functional/test_framework/blockfilter.py | 49 +++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 test/functional/test_framework/blockfilter.py diff --git a/test/functional/test_framework/blockfilter.py b/test/functional/test_framework/blockfilter.py new file mode 100644 index 00000000000..a30e37ea5bb --- /dev/null +++ b/test/functional/test_framework/blockfilter.py @@ -0,0 +1,49 @@ +#!/usr/bin/env python3 +# Copyright (c) 2022 The Bitcoin Core developers +# Distributed under the MIT software license, see the accompanying +# file COPYING or http://www.opensource.org/licenses/mit-license.php. +"""Helper routines relevant for compact block filters (BIP158). +""" +from .siphash import siphash + + +def bip158_basic_element_hash(script_pub_key, N, block_hash): + """ Calculates the ranged hash of a filter element as defined in BIP158: + + 'The first step in the filter construction is hashing the variable-sized + raw items in the set to the range [0, F), where F = N * M.' + + 'The items are first passed through the pseudorandom function SipHash, which takes a + 128-bit key k and a variable-sized byte vector and produces a uniformly random 64-bit + output. Implementations of this BIP MUST use the SipHash parameters c = 2 and d = 4.' + + 'The parameter k MUST be set to the first 16 bytes of the hash (in standard + little-endian representation) of the block for which the filter is constructed. This + ensures the key is deterministic while still varying from block to block.' + """ + M = 784931 + block_hash_bytes = bytes.fromhex(block_hash)[::-1] + k0 = int.from_bytes(block_hash_bytes[0:8], 'little') + k1 = int.from_bytes(block_hash_bytes[8:16], 'little') + return (siphash(k0, k1, script_pub_key) * (N * M)) >> 64 + + +def bip158_relevant_scriptpubkeys(node, block_hash): + """ Determines the basic filter relvant scriptPubKeys as defined in BIP158: + + 'A basic filter MUST contain exactly the following items for each transaction in a block: + - The previous output script (the script being spent) for each input, except for + the coinbase transaction. + - The scriptPubKey of each output, aside from all OP_RETURN output scripts.' + """ + spks = set() + for tx in node.getblock(blockhash=block_hash, verbosity=3)['tx']: + # gather prevout scripts + for i in tx['vin']: + if 'prevout' in i: + spks.add(bytes.fromhex(i['prevout']['scriptPubKey']['hex'])) + # gather output scripts + for o in tx['vout']: + if o['scriptPubKey']['type'] != 'nulldata': + spks.add(bytes.fromhex(o['scriptPubKey']['hex'])) + return spks