Bitcoin Core Fuzz Coverage Report

// Copyright (c) 2010 Satoshi Nakamoto

// Copyright (c) 2009-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 <kernel/chainparams.h>

#include <chainparamsseeds.h>

#include <consensus/amount.h>

#include <consensus/merkle.h>

#include <consensus/params.h>

#include <crypto/hex_base.h>

#include <hash.h>

#include <kernel/messagestartchars.h>

#include <primitives/block.h>

#include <primitives/transaction.h>

#include <script/interpreter.h>

#include <script/script.h>

#include <uint256.h>

#include <util/chaintype.h>

#include <util/log.h>

#include <util/strencodings.h>

#include <algorithm>

#include <array>

#include <cassert>

#include <cstdint>

#include <cstring>

#include <iterator>

#include <map>

#include <span>

#include <utility>

using namespace util::hex_literals;

static CBlock CreateGenesisBlock(const char* pszTimestamp, const CScript& genesisOutputScript, uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)

{

    CMutableTransaction txNew;

    txNew.version = 1;

    txNew.vin.resize(1);

    txNew.vout.resize(1);

    txNew.vin[0].scriptSig = CScript() << 486604799 << CScriptNum(4) << std::vector<unsigned char>((const unsigned char*)pszTimestamp, (const unsigned char*)pszTimestamp + strlen(pszTimestamp));

    txNew.vout[0].nValue = genesisReward;

    txNew.vout[0].scriptPubKey = genesisOutputScript;

    CBlock genesis;

    genesis.nTime    = nTime;

    genesis.nBits    = nBits;

    genesis.nNonce   = nNonce;

    genesis.nVersion = nVersion;

    genesis.vtx.push_back(MakeTransactionRef(std::move(txNew)));

    genesis.hashPrevBlock.SetNull();

    genesis.hashMerkleRoot = BlockMerkleRoot(genesis);

    return genesis;

}

/**

 * Build the genesis block. Note that the output of its generation

 * transaction cannot be spent since it did not originally exist in the

 * database.

 *

 * CBlock(hash=000000000019d6, ver=1, hashPrevBlock=00000000000000, hashMerkleRoot=4a5e1e, nTime=1231006505, nBits=1d00ffff, nNonce=2083236893, vtx=1)

 *   CTransaction(hash=4a5e1e, ver=1, vin.size=1, vout.size=1, nLockTime=0)

 *     CTxIn(COutPoint(000000, -1), coinbase 04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73)

 *     CTxOut(nValue=50.00000000, scriptPubKey=0x5F1DF16B2B704C8A578D0B)

 *   vMerkleTree: 4a5e1e

 */

static CBlock CreateGenesisBlock(uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)

{

    const char* pszTimestamp = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks";

    const CScript genesisOutputScript = CScript() << "04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f"_hex << OP_CHECKSIG;

    return CreateGenesisBlock(pszTimestamp, genesisOutputScript, nTime, nNonce, nBits, nVersion, genesisReward);

}

/**

 * Main network on which people trade goods and services.

 */

class CMainParams : public CChainParams {

public:

    CMainParams() {

        m_chain_type = ChainType::MAIN;

        consensus.signet_blocks = false;

        consensus.signet_challenge.clear();

        consensus.nSubsidyHalvingInterval = 210000;

        consensus.script_flag_exceptions.emplace( // BIP16 exception

            uint256{"00000000000002dc756eebf4f49723ed8d30cc28a5f108eb94b1ba88ac4f9c22"}, SCRIPT_VERIFY_NONE);

        consensus.script_flag_exceptions.emplace( // Taproot exception

            uint256{"0000000000000000000f14c35b2d841e986ab5441de8c585d5ffe55ea1e395ad"}, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS);

        consensus.BIP34Height = 227931;

        consensus.BIP34Hash = uint256{"000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8"};

        consensus.BIP65Height = 388381; // 000000000000000004c2b624ed5d7756c508d90fd0da2c7c679febfa6c4735f0

        consensus.BIP66Height = 363725; // 00000000000000000379eaa19dce8c9b722d46ae6a57c2f1a988119488b50931

        consensus.CSVHeight = 419328; // 000000000000000004a1b34462cb8aeebd5799177f7a29cf28f2d1961716b5b5

        consensus.SegwitHeight = 481824; // 0000000000000000001c8018d9cb3b742ef25114f27563e3fc4a1902167f9893

        consensus.MinBIP9WarningHeight = 711648; // taproot activation height + miner confirmation window

        consensus.powLimit = uint256{"00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};

        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks

        consensus.nPowTargetSpacing = 10 * 60;

        consensus.fPowAllowMinDifficultyBlocks = false;

        consensus.enforce_BIP94 = false;

        consensus.fPowNoRetargeting = false;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1815; // 90%

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        consensus.nMinimumChainWork = uint256{"0000000000000000000000000000000000000001128750f82f4c366153a3a030"};

        consensus.defaultAssumeValid = uint256{"00000000000000000000ccebd6d74d9194d8dcdc1d177c478e094bfad51ba5ac"}; // 938343

        /**

         * The message start string is designed to be unlikely to occur in normal data.

         * The characters are rarely used upper ASCII, not valid as UTF-8, and produce

         * a large 32-bit integer with any alignment.

         */

        pchMessageStart[0] = 0xf9;

        pchMessageStart[1] = 0xbe;

        pchMessageStart[2] = 0xb4;

        pchMessageStart[3] = 0xd9;

        nDefaultPort = 8333;

        nPruneAfterHeight = 100000;

        m_assumed_blockchain_size = 856;

        m_assumed_chain_state_size = 14;

        genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);

        consensus.hashGenesisBlock = genesis.GetHash();

        assert(consensus.hashGenesisBlock == uint256{"000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"});

        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        // Note that of those which support the service bits prefix, most only support a subset of

        // possible options.

        // This is fine at runtime as we'll fall back to using them as an addrfetch if they don't support the

        // service bits we want, but we should get them updated to support all service bits wanted by any

        // release ASAP to avoid it where possible.

        vSeeds.emplace_back("seed.bitcoin.sipa.be."); // Pieter Wuille, only supports x1, x5, x9, and xd

        vSeeds.emplace_back("dnsseed.bluematt.me."); // Matt Corallo, only supports x9

        vSeeds.emplace_back("seed.bitcoin.jonasschnelli.ch."); // Jonas Schnelli, only supports x1, x5, x9, and xd

        vSeeds.emplace_back("seed.btc.petertodd.net."); // Peter Todd, only supports x1, x5, x9, and xd

        vSeeds.emplace_back("seed.bitcoin.sprovoost.nl."); // Sjors Provoost

        vSeeds.emplace_back("dnsseed.emzy.de."); // Stephan Oeste

        vSeeds.emplace_back("seed.bitcoin.wiz.biz."); // Jason Maurice

        vSeeds.emplace_back("seed.mainnet.achownodes.xyz."); // Ava Chow, only supports x1, x5, x9, x49, x809, x849, xd, x400, x404, x408, x448, xc08, xc48, x40c

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,0);

        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,5);

        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,128);

        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x88, 0xB2, 0x1E};

        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x88, 0xAD, 0xE4};

        bech32_hrp = "bc";

        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_main), std::end(chainparams_seed_main));

        fDefaultConsistencyChecks = false;

        m_is_mockable_chain = false;

        m_assumeutxo_data = {

            {

                .height = 840'000,

                .hash_serialized = AssumeutxoHash{uint256{"a2a5521b1b5ab65f67818e5e8eccabb7171a517f9e2382208f77687310768f96"}},

                .m_chain_tx_count = 991032194,

                .blockhash = uint256{"0000000000000000000320283a032748cef8227873ff4872689bf23f1cda83a5"},

            },

            {

                .height = 880'000,

                .hash_serialized = AssumeutxoHash{uint256{"dbd190983eaf433ef7c15f78a278ae42c00ef52e0fd2a54953782175fbadcea9"}},

                .m_chain_tx_count = 1145604538,

                .blockhash = uint256{"000000000000000000010b17283c3c400507969a9c2afd1dcf2082ec5cca2880"},

            },

            {

                .height = 910'000,

                .hash_serialized = AssumeutxoHash{uint256{"4daf8a17b4902498c5787966a2b51c613acdab5df5db73f196fa59a4da2f1568"}},

                .m_chain_tx_count = 1226586151,

                .blockhash = uint256{"0000000000000000000108970acb9522ffd516eae17acddcb1bd16469194a821"},

            },

            {

                .height = 935'000,

                .hash_serialized = AssumeutxoHash{uint256{"e4b90ef9eae834f56c4b64d2d50143cee10ad87994c614d7d04125e2a6025050"}},

                .m_chain_tx_count = 1305397408,

                .blockhash = uint256{"0000000000000000000147034958af1652b2b91bba607beacc5e72a56f0fb5ee"},

            }

        };

        chainTxData = ChainTxData{

            // Data from RPC: getchaintxstats 4096 00000000000000000000ccebd6d74d9194d8dcdc1d177c478e094bfad51ba5ac

            .nTime    = 1772055173,

            .tx_count = 1315805869,

            .dTxRate  = 5.40111006496122,

        };

        // Generated by headerssync-params.py on 2026-02-25.

        m_headers_sync_params = HeadersSyncParams{

            .commitment_period = 641,

            .redownload_buffer_size = 15218, // 15218/641 = ~23.7 commitments

        };

    }

};

/**

 * Testnet (v3): public test network which is reset from time to time.

 */

class CTestNetParams : public CChainParams {

public:

    CTestNetParams() {

        m_chain_type = ChainType::TESTNET;

        consensus.signet_blocks = false;

        consensus.signet_challenge.clear();

        consensus.nSubsidyHalvingInterval = 210000;

        consensus.script_flag_exceptions.emplace( // BIP16 exception

            uint256{"00000000dd30457c001f4095d208cc1296b0eed002427aa599874af7a432b105"}, SCRIPT_VERIFY_NONE);

        consensus.BIP34Height = 21111;

        consensus.BIP34Hash = uint256{"0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8"};

        consensus.BIP65Height = 581885; // 00000000007f6655f22f98e72ed80d8b06dc761d5da09df0fa1dc4be4f861eb6

        consensus.BIP66Height = 330776; // 000000002104c8c45e99a8853285a3b592602a3ccde2b832481da85e9e4ba182

        consensus.CSVHeight = 770112; // 00000000025e930139bac5c6c31a403776da130831ab85be56578f3fa75369bb

        consensus.SegwitHeight = 834624; // 00000000002b980fcd729daaa248fd9316a5200e9b367f4ff2c42453e84201ca

        consensus.MinBIP9WarningHeight = 2013984; // taproot activation height + miner confirmation window

        consensus.powLimit = uint256{"00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};

        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks

        consensus.nPowTargetSpacing = 10 * 60;

        consensus.fPowAllowMinDifficultyBlocks = true;

        consensus.enforce_BIP94 = false;

        consensus.fPowNoRetargeting = false;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1512; // 75%

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        consensus.nMinimumChainWork = uint256{"0000000000000000000000000000000000000000000017dde1c649f3708d14b6"};

        consensus.defaultAssumeValid = uint256{"000000007a61e4230b28ac5cb6b5e5a0130de37ac1faf2f8987d2fa6505b67f4"}; // 4842348

        pchMessageStart[0] = 0x0b;

        pchMessageStart[1] = 0x11;

        pchMessageStart[2] = 0x09;

        pchMessageStart[3] = 0x07;

        nDefaultPort = 18333;

        nPruneAfterHeight = 1000;

        m_assumed_blockchain_size = 245;

        m_assumed_chain_state_size = 19;

        genesis = CreateGenesisBlock(1296688602, 414098458, 0x1d00ffff, 1, 50 * COIN);

        consensus.hashGenesisBlock = genesis.GetHash();

        assert(consensus.hashGenesisBlock == uint256{"000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943"});

        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        vFixedSeeds.clear();

        vSeeds.clear();

        // nodes with support for servicebits filtering should be at the top

        vSeeds.emplace_back("testnet-seed.bitcoin.jonasschnelli.ch.");

        vSeeds.emplace_back("seed.tbtc.petertodd.net.");

        vSeeds.emplace_back("seed.testnet.bitcoin.sprovoost.nl.");

        vSeeds.emplace_back("testnet-seed.bluematt.me."); // Just a static list of stable node(s), only supports x9

        vSeeds.emplace_back("seed.testnet.achownodes.xyz."); // Ava Chow, only supports x1, x5, x9, x49, x809, x849, xd, x400, x404, x408, x448, xc08, xc48, x40c

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);

        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);

        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);

        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};

        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "tb";

        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_test), std::end(chainparams_seed_test));

        fDefaultConsistencyChecks = false;

        m_is_mockable_chain = false;

        m_assumeutxo_data = {

            {

                .height = 2'500'000,

                .hash_serialized = AssumeutxoHash{uint256{"f841584909f68e47897952345234e37fcd9128cd818f41ee6c3ca68db8071be7"}},

                .m_chain_tx_count = 66484552,

                .blockhash = uint256{"0000000000000093bcb68c03a9a168ae252572d348a2eaeba2cdf9231d73206f"},

            },

            {

                .height = 4'840'000,

                .hash_serialized = AssumeutxoHash{uint256{"ce6bb677bb2ee9789c4a1c9d73e6683c53fc20e8fdbedbdaaf468982a0c8db2a"}},

                .m_chain_tx_count = 536078574,

                .blockhash = uint256{"00000000000000f4971a7fb37fbdff89315b69a2e1920c467654a382f0d64786"},

            }

        };

        chainTxData = ChainTxData{

            // Data from RPC: getchaintxstats 4096 000000007a61e4230b28ac5cb6b5e5a0130de37ac1faf2f8987d2fa6505b67f4

            .nTime    = 1772051651,

            .tx_count = 536108416,

            .dTxRate  = 0.02691479016257117,

        };

        // Generated by headerssync-params.py on 2026-02-25.

        m_headers_sync_params = HeadersSyncParams{

            .commitment_period = 673,

            .redownload_buffer_size = 14460, // 14460/673 = ~21.5 commitments

        };

    }

};

/**

 * Testnet (v4): public test network which is reset from time to time.

 */

class CTestNet4Params : public CChainParams {

public:

    CTestNet4Params() {

        m_chain_type = ChainType::TESTNET4;

        consensus.signet_blocks = false;

        consensus.signet_challenge.clear();

        consensus.nSubsidyHalvingInterval = 210000;

        consensus.BIP34Height = 1;

        consensus.BIP34Hash = uint256{};

        consensus.BIP65Height = 1;

        consensus.BIP66Height = 1;

        consensus.CSVHeight = 1;

        consensus.SegwitHeight = 1;

        consensus.MinBIP9WarningHeight = 0;

        consensus.powLimit = uint256{"00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};

        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks

        consensus.nPowTargetSpacing = 10 * 60;

        consensus.fPowAllowMinDifficultyBlocks = true;

        consensus.enforce_BIP94 = true;

        consensus.fPowNoRetargeting = false;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1512; // 75%

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        consensus.nMinimumChainWork = uint256{"0000000000000000000000000000000000000000000009a0fe15d0177d086304"};

        consensus.defaultAssumeValid = uint256{"0000000002368b1e4ee27e2e85676ae6f9f9e69579b29093e9a82c170bf7cf8a"}; // 123613

        pchMessageStart[0] = 0x1c;

        pchMessageStart[1] = 0x16;

        pchMessageStart[2] = 0x3f;

        pchMessageStart[3] = 0x28;

        nDefaultPort = 48333;

        nPruneAfterHeight = 1000;

        m_assumed_blockchain_size = 31;

        m_assumed_chain_state_size = 2;

        const char* testnet4_genesis_msg = "03/May/2024 000000000000000000001ebd58c244970b3aa9d783bb001011fbe8ea8e98e00e";

        const CScript testnet4_genesis_script = CScript() << "000000000000000000000000000000000000000000000000000000000000000000"_hex << OP_CHECKSIG;

        genesis = CreateGenesisBlock(testnet4_genesis_msg,

                testnet4_genesis_script,

                1714777860,

                393743547,

                0x1d00ffff,

                1,

                50 * COIN);

        consensus.hashGenesisBlock = genesis.GetHash();

        assert(consensus.hashGenesisBlock == uint256{"00000000da84f2bafbbc53dee25a72ae507ff4914b867c565be350b0da8bf043"});

        assert(genesis.hashMerkleRoot == uint256{"7aa0a7ae1e223414cb807e40cd57e667b718e42aaf9306db9102fe28912b7b4e"});

        vFixedSeeds.clear();

        vSeeds.clear();

        // nodes with support for servicebits filtering should be at the top

        vSeeds.emplace_back("seed.testnet4.bitcoin.sprovoost.nl."); // Sjors Provoost

        vSeeds.emplace_back("seed.testnet4.wiz.biz."); // Jason Maurice

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);

        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);

        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);

        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};

        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "tb";

        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_testnet4), std::end(chainparams_seed_testnet4));

        fDefaultConsistencyChecks = false;

        m_is_mockable_chain = false;

        m_assumeutxo_data = {

            {

                .height = 90'000,

                .hash_serialized = AssumeutxoHash{uint256{"784fb5e98241de66fdd429f4392155c9e7db5c017148e66e8fdbc95746f8b9b5"}},

                .m_chain_tx_count = 11347043,

                .blockhash = uint256{"0000000002ebe8bcda020e0dd6ccfbdfac531d2f6a81457191b99fc2df2dbe3b"},

            },

            {

                .height = 120'000,

                .hash_serialized = AssumeutxoHash{uint256{"10b05d05ad468d0971162e1b222a4aa66caca89da2bb2a93f8f37fb29c4794b0"}},

                .m_chain_tx_count = 14141057,

                .blockhash = uint256{"000000000bd2317e51b3c5794981c35ba894ce27d3e772d5c39ecd9cbce01dc8"},

            }

        };

        chainTxData = ChainTxData{

            // Data from RPC: getchaintxstats 4096 0000000002368b1e4ee27e2e85676ae6f9f9e69579b29093e9a82c170bf7cf8a

            .nTime    = 1772013387,

            .tx_count = 14191421,

            .dTxRate  = 0.01848579579528412,

        };

        // Generated by headerssync-params.py on 2026-02-25.

        m_headers_sync_params = HeadersSyncParams{

            .commitment_period = 606,

            .redownload_buffer_size = 16092, // 16092/606 = ~26.6 commitments

        };

    }

};

/**

 * Signet: test network with an additional consensus parameter (see BIP325).

 */

class SigNetParams : public CChainParams {

public:

    explicit SigNetParams(const SigNetOptions& options)

    {

        std::vector<uint8_t> bin;

        vFixedSeeds.clear();

        vSeeds.clear();

        if (!options.challenge) {

            bin = "512103ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d1e086be430210359ef5021964fe22d6f8e05b2463c9540ce96883fe3b278760f048f5189f2e6c452ae"_hex_v_u8;

            vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_signet), std::end(chainparams_seed_signet));

            vSeeds.emplace_back("seed.signet.bitcoin.sprovoost.nl.");

            vSeeds.emplace_back("seed.signet.achownodes.xyz."); // Ava Chow, only supports x1, x5, x9, x49, x809, x849, xd, x400, x404, x408, x448, xc08, xc48, x40c

            consensus.nMinimumChainWork = uint256{"00000000000000000000000000000000000000000000000000000b463ea0a4b8"};

            consensus.defaultAssumeValid = uint256{"00000008414aab61092ef93f1aacc54cf9e9f16af29ddad493b908a01ff5c329"}; // 293175

            m_assumed_blockchain_size = 24;

            m_assumed_chain_state_size = 4;

            chainTxData = ChainTxData{

                // Data from RPC: getchaintxstats 4096 00000008414aab61092ef93f1aacc54cf9e9f16af29ddad493b908a01ff5c329

                .nTime    = 1772055248,

                .tx_count = 28676833,

                .dTxRate  = 0.06736623436338929,

            };

        } else {

            bin = *options.challenge;

            consensus.nMinimumChainWork = uint256{};

            consensus.defaultAssumeValid = uint256{};

            m_assumed_blockchain_size = 0;

            m_assumed_chain_state_size = 0;

            chainTxData = ChainTxData{

                0,

                0,

                0,

            };

            LogInfo("Signet with challenge %s", HexStr(bin));

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#define LogInfo(...) LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Info, /*should_ratelimit=*/true, __VA_ARGS__)

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89

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#define LogPrintLevel_(category, level, should_ratelimit, ...) LogPrintFormatInternal(SourceLocation{__func__}, category, level, should_ratelimit, __VA_ARGS__)

        }

        if (options.seeds) {

            vSeeds = *options.seeds;

        }

        m_chain_type = ChainType::SIGNET;

        consensus.signet_blocks = true;

        consensus.signet_challenge.assign(bin.begin(), bin.end());

        consensus.nSubsidyHalvingInterval = 210000;

        consensus.BIP34Height = 1;

        consensus.BIP34Hash = uint256{};

        consensus.BIP65Height = 1;

        consensus.BIP66Height = 1;

        consensus.CSVHeight = 1;

        consensus.SegwitHeight = 1;

        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks

        consensus.nPowTargetSpacing = 10 * 60;

        consensus.fPowAllowMinDifficultyBlocks = false;

        consensus.enforce_BIP94 = false;

        consensus.fPowNoRetargeting = false;

        consensus.MinBIP9WarningHeight = 0;

        consensus.powLimit = uint256{"00000377ae000000000000000000000000000000000000000000000000000000"};

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 1815; // 90%

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 2016;

        // message start is defined as the first 4 bytes of the sha256d of the block script

        HashWriter h{};

        h << consensus.signet_challenge;

        uint256 hash = h.GetHash();

        std::copy_n(hash.begin(), 4, pchMessageStart.begin());

        nDefaultPort = 38333;

        nPruneAfterHeight = 1000;

        genesis = CreateGenesisBlock(1598918400, 52613770, 0x1e0377ae, 1, 50 * COIN);

        consensus.hashGenesisBlock = genesis.GetHash();

        assert(consensus.hashGenesisBlock == uint256{"00000008819873e925422c1ff0f99f7cc9bbb232af63a077a480a3633bee1ef6"});

        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        m_assumeutxo_data = {

            {

                .height = 160'000,

                .hash_serialized = AssumeutxoHash{uint256{"fe0a44309b74d6b5883d246cb419c6221bcccf0b308c9b59b7d70783dbdf928a"}},

                .m_chain_tx_count = 2289496,

                .blockhash = uint256{"0000003ca3c99aff040f2563c2ad8f8ec88bd0fd6b8f0895cfaf1ef90353a62c"},

            },

            {

                .height = 290'000,

                .hash_serialized = AssumeutxoHash{uint256{"97267e000b4b876800167e71b9123f1529d13b14308abec2888bbd2160d14545"}},

                .m_chain_tx_count = 28547497,

                .blockhash = uint256{"0000000577f2741bb30cd9d39d6d71b023afbeb9764f6260786a97969d5c9ac0"},

            }

        };

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);

        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);

        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);

        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};

        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "tb";

        fDefaultConsistencyChecks = false;

        m_is_mockable_chain = false;

        // Generated by headerssync-params.py on 2026-02-25.

        m_headers_sync_params = HeadersSyncParams{

            .commitment_period = 620,

            .redownload_buffer_size = 15724, // 15724/620 = ~25.4 commitments

        };

    }

};

/**

 * Regression test: intended for private networks only. Has minimal difficulty to ensure that

 * blocks can be found instantly.

 */

class CRegTestParams : public CChainParams

{

public:

    explicit CRegTestParams(const RegTestOptions& opts)

    {

        m_chain_type = ChainType::REGTEST;

        consensus.signet_blocks = false;

        consensus.signet_challenge.clear();

        consensus.nSubsidyHalvingInterval = 150;

        consensus.BIP34Height = 1; // Always active unless overridden

        consensus.BIP34Hash = uint256();

        consensus.BIP65Height = 1;  // Always active unless overridden

        consensus.BIP66Height = 1;  // Always active unless overridden

        consensus.CSVHeight = 1;    // Always active unless overridden

        consensus.SegwitHeight = 0; // Always active unless overridden

        consensus.MinBIP9WarningHeight = 0;

        consensus.powLimit = uint256{"7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"};

        consensus.nPowTargetTimespan = 24 * 60 * 60; // one day

        consensus.nPowTargetSpacing = 10 * 60;

        consensus.fPowAllowMinDifficultyBlocks = true;

        consensus.enforce_BIP94 = opts.enforce_bip94;

        consensus.fPowNoRetargeting = true;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 0;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].threshold = 108; // 75%

        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].period = 144; // Faster than normal for regtest (144 instead of 2016)

        consensus.nMinimumChainWork = uint256{};

        consensus.defaultAssumeValid = uint256{};

        pchMessageStart[0] = 0xfa;

        pchMessageStart[1] = 0xbf;

        pchMessageStart[2] = 0xb5;

        pchMessageStart[3] = 0xda;

        nDefaultPort = 18444;

        nPruneAfterHeight = opts.fastprune ? 100 : 1000;

        m_assumed_blockchain_size = 0;

        m_assumed_chain_state_size = 0;

        for (const auto& [dep, height] : opts.activation_heights) {

            switch (dep) {

            case Consensus::BuriedDeployment::DEPLOYMENT_SEGWIT:

                consensus.SegwitHeight = int{height};

                break;

            case Consensus::BuriedDeployment::DEPLOYMENT_HEIGHTINCB:

                consensus.BIP34Height = int{height};

                break;

            case Consensus::BuriedDeployment::DEPLOYMENT_DERSIG:

                consensus.BIP66Height = int{height};

                break;

            case Consensus::BuriedDeployment::DEPLOYMENT_CLTV:

                consensus.BIP65Height = int{height};

                break;

            case Consensus::BuriedDeployment::DEPLOYMENT_CSV:

                consensus.CSVHeight = int{height};

                break;

            }

        }

        for (const auto& [deployment_pos, version_bits_params] : opts.version_bits_parameters) {

            consensus.vDeployments[deployment_pos].nStartTime = version_bits_params.start_time;

            consensus.vDeployments[deployment_pos].nTimeout = version_bits_params.timeout;

            consensus.vDeployments[deployment_pos].min_activation_height = version_bits_params.min_activation_height;

        }

        genesis = CreateGenesisBlock(1296688602, 2, 0x207fffff, 1, 50 * COIN);

        consensus.hashGenesisBlock = genesis.GetHash();

        assert(consensus.hashGenesisBlock == uint256{"0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"});

        assert(genesis.hashMerkleRoot == uint256{"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"});

        vFixedSeeds.clear(); //!< Regtest mode doesn't have any fixed seeds.

        vSeeds.clear();

        vSeeds.emplace_back("dummySeed.invalid.");

        fDefaultConsistencyChecks = true;

        m_is_mockable_chain = true;

        m_assumeutxo_data = {

            {   // For use by unit tests

                .height = 110,

                .hash_serialized = AssumeutxoHash{uint256{"b952555c8ab81fec46f3d4253b7af256d766ceb39fb7752b9d18cdf4a0141327"}},

                .m_chain_tx_count = 111,

                .blockhash = uint256{"6affe030b7965ab538f820a56ef56c8149b7dc1d1c144af57113be080db7c397"},

            },

            {

                // For use by fuzz target src/test/fuzz/utxo_snapshot.cpp

                .height = 200,

                .hash_serialized = AssumeutxoHash{uint256{"17dcc016d188d16068907cdeb38b75691a118d43053b8cd6a25969419381d13a"}},

                .m_chain_tx_count = 201,

                .blockhash = uint256{"385901ccbd69dff6bbd00065d01fb8a9e464dede7cfe0372443884f9b1dcf6b9"},

            },

            {

                // For use by test/functional/feature_assumeutxo.py and test/functional/tool_bitcoin_chainstate.py

                .height = 299,

                .hash_serialized = AssumeutxoHash{uint256{"d2b051ff5e8eef46520350776f4100dd710a63447a8e01d917e92e79751a63e2"}},

                .m_chain_tx_count = 334,

                .blockhash = uint256{"7cc695046fec709f8c9394b6f928f81e81fd3ac20977bb68760fa1faa7916ea2"},

            },

        };

        chainTxData = ChainTxData{

            .nTime = 0,

            .tx_count = 0,

            .dTxRate = 0.001, // Set a non-zero rate to make it testable

        };

        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);

        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);

        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);

        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};

        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};

        bech32_hrp = "bcrt";

        // Copied from Testnet4.

        m_headers_sync_params = HeadersSyncParams{

            .commitment_period = 275,

            .redownload_buffer_size = 7017, // 7017/275 = ~25.5 commitments

        };

    }

};

std::unique_ptr<const CChainParams> CChainParams::SigNet(const SigNetOptions& options)

{

    return std::make_unique<const SigNetParams>(options);

}

std::unique_ptr<const CChainParams> CChainParams::RegTest(const RegTestOptions& options)

{

    return std::make_unique<const CRegTestParams>(options);

}

std::unique_ptr<const CChainParams> CChainParams::Main()

{

    return std::make_unique<const CMainParams>();

}

std::unique_ptr<const CChainParams> CChainParams::TestNet()

{

    return std::make_unique<const CTestNetParams>();

}

std::unique_ptr<const CChainParams> CChainParams::TestNet4()

{

    return std::make_unique<const CTestNet4Params>();

}

std::vector<int> CChainParams::GetAvailableSnapshotHeights() const

{

    std::vector<int> heights;

    heights.reserve(m_assumeutxo_data.size());

    for (const auto& data : m_assumeutxo_data) {

        heights.emplace_back(data.height);

    }

    return heights;

}

std::optional<ChainType> GetNetworkForMagic(const MessageStartChars& message)

{

    const auto mainnet_msg = CChainParams::Main()->MessageStart();

    const auto testnet_msg = CChainParams::TestNet()->MessageStart();

    const auto testnet4_msg = CChainParams::TestNet4()->MessageStart();

    const auto regtest_msg = CChainParams::RegTest({})->MessageStart();

    const auto signet_msg = CChainParams::SigNet({})->MessageStart();

    if (std::ranges::equal(message, mainnet_msg)) {

        return ChainType::MAIN;

    } else if (std::ranges::equal(message, testnet_msg)) {

        return ChainType::TESTNET;

    } else if (std::ranges::equal(message, testnet4_msg)) {

        return ChainType::TESTNET4;

    } else if (std::ranges::equal(message, regtest_msg)) {

        return ChainType::REGTEST;

    } else if (std::ranges::equal(message, signet_msg)) {

        return ChainType::SIGNET;

    }

    return std::nullopt;

}