// Copyright (c) 2009-present The Bitcoin Core developers

// Copyright (c) 2017 The Zcash developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <key.h>

#include <crypto/common.h>

#include <crypto/hmac_sha512.h>

#include <hash.h>

#include <random.h>

#include <secp256k1.h>

#include <secp256k1_ellswift.h>

#include <secp256k1_extrakeys.h>

#include <secp256k1_musig.h>

#include <secp256k1_recovery.h>

#include <secp256k1_schnorrsig.h>

static secp256k1_context* secp256k1_context_sign = nullptr;

/** These functions are taken from the libsecp256k1 distribution and are very ugly. */

/**

 * This parses a format loosely based on a DER encoding of the ECPrivateKey type from

 * section C.4 of SEC 1 <https://www.secg.org/sec1-v2.pdf>, with the following caveats:

 *

 * * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not

 *   required to be encoded as one octet if it is less than 256, as DER would require.

 * * The octet-length of the SEQUENCE must not be greater than the remaining

 *   length of the key encoding, but need not match it (i.e. the encoding may contain

 *   junk after the encoded SEQUENCE).

 * * The privateKey OCTET STRING is zero-filled on the left to 32 octets.

 * * Anything after the encoding of the privateKey OCTET STRING is ignored, whether

 *   or not it is validly encoded DER.

 *

 * out32 must point to an output buffer of length at least 32 bytes.

 */

int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *seckey, size_t seckeylen) {

    const unsigned char *end = seckey + seckeylen;

    memset(out32, 0, 32);

    /* sequence header */

    if (end - seckey < 1 || *seckey != 0x30u) {

        return 0;

    }

    seckey++;

    /* sequence length constructor */

    if (end - seckey < 1 || !(*seckey & 0x80u)) {

        return 0;

    }

    ptrdiff_t lenb = *seckey & ~0x80u; seckey++;

    if (lenb < 1 || lenb > 2) {

        return 0;

    }

    if (end - seckey < lenb) {

        return 0;

    }

    /* sequence length */

    ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u);

    seckey += lenb;

    if (end - seckey < len) {

        return 0;

    }

    /* sequence element 0: version number (=1) */

    if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) {

        return 0;

    }

    seckey += 3;

    /* sequence element 1: octet string, up to 32 bytes */

    if (end - seckey < 2 || seckey[0] != 0x04u) {

        return 0;

    }

    ptrdiff_t oslen = seckey[1];

    seckey += 2;

    if (oslen > 32 || end - seckey < oslen) {

        return 0;

    }

    memcpy(out32 + (32 - oslen), seckey, oslen);

    if (!secp256k1_ec_seckey_verify(ctx, out32)) {

        memset(out32, 0, 32);

        return 0;

    }

    return 1;

}

/**

 * This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1

 * <https://www.secg.org/sec1-v2.pdf>. The optional parameters and publicKey fields are

 * included.

 *

 * seckey must point to an output buffer of length at least CKey::SIZE bytes.

 * seckeylen must initially be set to the size of the seckey buffer. Upon return it

 * will be set to the number of bytes used in the buffer.

 * key32 must point to a 32-byte raw private key.

 */

int ec_seckey_export_der(const secp256k1_context *ctx, unsigned char *seckey, size_t *seckeylen, const unsigned char *key32, bool compressed) {

    assert(*seckeylen >= CKey::SIZE);

    secp256k1_pubkey pubkey;

    size_t pubkeylen = 0;

    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {

        *seckeylen = 0;

        return 0;

    }

    if (compressed) {

        static const unsigned char begin[] = {

            0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20

        };

        static const unsigned char middle[] = {

            0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,

            0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,

            0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,

            0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,

            0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,

            0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,

            0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,

            0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,

            0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00

        };

        unsigned char *ptr = seckey;

        memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);

        memcpy(ptr, key32, 32); ptr += 32;

        memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);

        pubkeylen = CPubKey::COMPRESSED_SIZE;

        secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);

        ptr += pubkeylen;

        *seckeylen = ptr - seckey;

        assert(*seckeylen == CKey::COMPRESSED_SIZE);

    } else {

        static const unsigned char begin[] = {

            0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20

        };

        static const unsigned char middle[] = {

            0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,

            0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,

            0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,

            0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,

            0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,

            0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,

            0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,

            0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,

            0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,

            0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,

            0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00

        };

        unsigned char *ptr = seckey;

        memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);

        memcpy(ptr, key32, 32); ptr += 32;

        memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);

        pubkeylen = CPubKey::SIZE;

        secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);

        ptr += pubkeylen;

        *seckeylen = ptr - seckey;

        assert(*seckeylen == CKey::SIZE);

    }

    return 1;

}

bool CKey::Check(const unsigned char *vch) {

    return secp256k1_ec_seckey_verify(secp256k1_context_static, vch);

}

void CKey::MakeNewKey(bool fCompressedIn) {

    MakeKeyData();

    do {

        GetStrongRandBytes(*keydata);

    } while (!Check(keydata->data()));

    fCompressed = fCompressedIn;

}

CPrivKey CKey::GetPrivKey() const {

    assert(keydata);

    CPrivKey seckey;

    int ret;

    size_t seckeylen;

    seckey.resize(SIZE);

    seckeylen = SIZE;

    ret = ec_seckey_export_der(secp256k1_context_sign, seckey.data(), &seckeylen, UCharCast(begin()), fCompressed);

    assert(ret);

    seckey.resize(seckeylen);

    return seckey;

}

CPubKey CKey::GetPubKey() const {

    assert(keydata);

    secp256k1_pubkey pubkey;

    size_t clen = CPubKey::SIZE;

    CPubKey result;

    int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, UCharCast(begin()));

    assert(ret);

    secp256k1_ec_pubkey_serialize(secp256k1_context_static, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);

    assert(result.size() == clen);

    assert(result.IsValid());

    return result;

}

// Check that the sig has a low R value and will be less than 71 bytes

bool SigHasLowR(const secp256k1_ecdsa_signature* sig)

{

    unsigned char compact_sig[64];

    secp256k1_ecdsa_signature_serialize_compact(secp256k1_context_static, compact_sig, sig);

    // In DER serialization, all values are interpreted as big-endian, signed integers. The highest bit in the integer indicates

    // its signed-ness; 0 is positive, 1 is negative. When the value is interpreted as a negative integer, it must be converted

    // to a positive value by prepending a 0x00 byte so that the highest bit is 0. We can avoid this prepending by ensuring that

    // our highest bit is always 0, and thus we must check that the first byte is less than 0x80.

    return compact_sig[0] < 0x80;

}

bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool grind, uint32_t test_case) const {

    if (!keydata)

        return false;

    vchSig.resize(CPubKey::SIGNATURE_SIZE);

    size_t nSigLen = CPubKey::SIGNATURE_SIZE;

    unsigned char extra_entropy[32] = {0};

    WriteLE32(extra_entropy, test_case);

    secp256k1_ecdsa_signature sig;

    uint32_t counter = 0;

    int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), UCharCast(begin()), secp256k1_nonce_function_rfc6979, (!grind && test_case) ? extra_entropy : nullptr);

    // Grind for low R

    while (ret && !SigHasLowR(&sig) && grind) {

        WriteLE32(extra_entropy, ++counter);

        ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), UCharCast(begin()), secp256k1_nonce_function_rfc6979, extra_entropy);

    }

    assert(ret);

    secp256k1_ecdsa_signature_serialize_der(secp256k1_context_static, vchSig.data(), &nSigLen, &sig);

    vchSig.resize(nSigLen);

    // Additional verification step to prevent using a potentially corrupted signature

    secp256k1_pubkey pk;

    ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pk, UCharCast(begin()));

    assert(ret);

    ret = secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pk);

    assert(ret);

    return true;

}

bool CKey::VerifyPubKey(const CPubKey& pubkey) const {

    if (pubkey.IsCompressed() != fCompressed) {

        return false;

    }

    unsigned char rnd[8];

    std::string str = "Bitcoin key verification\n";

    GetRandBytes(rnd);

    uint256 hash{Hash(str, rnd)};

    std::vector<unsigned char> vchSig;

    Sign(hash, vchSig);

    return pubkey.Verify(hash, vchSig);

}

bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {

    if (!keydata)

        return false;

    vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE);

    int rec = -1;

    secp256k1_ecdsa_recoverable_signature rsig;

    int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &rsig, hash.begin(), UCharCast(begin()), secp256k1_nonce_function_rfc6979, nullptr);

    assert(ret);

    ret = secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_static, &vchSig[1], &rec, &rsig);

    assert(ret);

    assert(rec != -1);

    vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);

    // Additional verification step to prevent using a potentially corrupted signature

    secp256k1_pubkey epk, rpk;

    ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &epk, UCharCast(begin()));

    assert(ret);

    ret = secp256k1_ecdsa_recover(secp256k1_context_static, &rpk, &rsig, hash.begin());

    assert(ret);

    ret = secp256k1_ec_pubkey_cmp(secp256k1_context_static, &epk, &rpk);

    assert(ret == 0);

    return true;

}

bool CKey::SignSchnorr(const uint256& hash, std::span<unsigned char> sig, const uint256* merkle_root, const uint256& aux) const

{

    KeyPair kp = ComputeKeyPair(merkle_root);

    return kp.SignSchnorr(hash, sig, aux);

}

bool CKey::Load(const CPrivKey &seckey, const CPubKey &vchPubKey, bool fSkipCheck=false) {

    MakeKeyData();

    if (!ec_seckey_import_der(secp256k1_context_static, (unsigned char*)begin(), seckey.data(), seckey.size())) {

        ClearKeyData();

        return false;

    }

    fCompressed = vchPubKey.IsCompressed();

    if (fSkipCheck)

        return true;

    return VerifyPubKey(vchPubKey);

}

bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {

    assert(IsValid());

    assert(IsCompressed());

    std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);

    if ((nChild >> 31) == 0) {

        CPubKey pubkey = GetPubKey();

        assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);

        BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());

    } else {

        assert(size() == 32);

        BIP32Hash(cc, nChild, 0, UCharCast(begin()), vout.data());

    }

    memcpy(ccChild.begin(), vout.data()+32, 32);

    keyChild.Set(begin(), begin() + 32, true);

    bool ret = secp256k1_ec_seckey_tweak_add(secp256k1_context_static, (unsigned char*)keyChild.begin(), vout.data());

    if (!ret) keyChild.ClearKeyData();

    return ret;

}

EllSwiftPubKey CKey::EllSwiftCreate(std::span<const std::byte> ent32) const

{

    assert(keydata);

    assert(ent32.size() == 32);

    std::array<std::byte, EllSwiftPubKey::size()> encoded_pubkey;

    auto success = secp256k1_ellswift_create(secp256k1_context_sign,

                                             UCharCast(encoded_pubkey.data()),

                                             keydata->data(),

                                             UCharCast(ent32.data()));

    // Should always succeed for valid keys (asserted above).

    assert(success);

    return {encoded_pubkey};

}

ECDHSecret CKey::ComputeBIP324ECDHSecret(const EllSwiftPubKey& their_ellswift, const EllSwiftPubKey& our_ellswift, bool initiating) const

{

    assert(keydata);

    ECDHSecret output;

    // BIP324 uses the initiator as party A, and the responder as party B. Remap the inputs

    // accordingly:

    bool success = secp256k1_ellswift_xdh(secp256k1_context_static,

                                          UCharCast(output.data()),

                                          UCharCast(initiating ? our_ellswift.data() : their_ellswift.data()),

                                          UCharCast(initiating ? their_ellswift.data() : our_ellswift.data()),

                                          keydata->data(),

                                          initiating ? 0 : 1,

                                          secp256k1_ellswift_xdh_hash_function_bip324,

                                          nullptr);

    // Should always succeed for valid keys (assert above).

    assert(success);

    return output;

}

KeyPair CKey::ComputeKeyPair(const uint256* merkle_root) const

{

    return KeyPair(*this, merkle_root);

}

std::vector<uint8_t> CKey::CreateMuSig2Nonce(MuSig2SecNonce& secnonce, const uint256& sighash, const CPubKey& aggregate_pubkey, const std::vector<CPubKey>& pubkeys)

{

    // Get the keyagg cache and aggregate pubkey

    secp256k1_musig_keyagg_cache keyagg_cache;

    if (!MuSig2AggregatePubkeys(pubkeys, keyagg_cache, aggregate_pubkey)) return {};

    // Parse participant pubkey

    CPubKey our_pubkey = GetPubKey();

    secp256k1_pubkey pubkey;

    if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &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, sighash.data(), &keyagg_cache, nullptr)) {

        return {};

    }

    // Serialize pubnonce

    std::vector<uint8_t> out;

    out.resize(MUSIG2_PUBNONCE_SIZE);

    if (!secp256k1_musig_pubnonce_serialize(secp256k1_context_static, out.data(), &pubnonce)) {

        return {};

    }

    return out;

}

std::optional<uint256> CKey::CreateMuSig2PartialSig(const uint256& sighash, 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 (!MuSig2AggregatePubkeys(pubkeys, keyagg_cache, aggregate_pubkey)) return std::nullopt;

    // Check that there are enough pubnonces

    if (pubnonces.size() != pubkeys.size()) 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;

    std::optional<size_t> our_pubkey_idx;

    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() != MUSIG2_PUBNONCE_SIZE) return std::nullopt;

        if (part_pk == our_pubkey) {

            our_pubkey_idx = signers_data.size();

        }

        auto& [secp_pk, secp_pn] = 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 (our_pubkey_idx == std::nullopt) {

        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_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;

    }

    // Create partial signature

    secp256k1_musig_partial_sig psig;

    if (!secp256k1_musig_partial_sign(secp256k1_context_static, &psig, secnonce.Get(), &keypair, &keyagg_cache, &session)) {

        return std::nullopt;

    }

    // The secnonce must be deleted after signing to prevent nonce reuse.

    secnonce.Invalidate();

    // Verify partial signature

    if (!secp256k1_musig_partial_sig_verify(secp256k1_context_static, &psig, &(signers_data.at(*our_pubkey_idx).second), &(signers_data.at(*our_pubkey_idx).first), &keyagg_cache, &session)) {

        return std::nullopt;

    }

    // Serialize

    uint256 sig;

    if (!secp256k1_musig_partial_sig_serialize(secp256k1_context_static, sig.data(), &psig)) {

        return std::nullopt;

    }

    return sig;

}

CKey GenerateRandomKey(bool compressed) noexcept

{

    CKey key;

    key.MakeNewKey(/*fCompressed=*/compressed);

    return key;

}

bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {

    if (nDepth == std::numeric_limits<unsigned char>::max()) return false;

    out.nDepth = nDepth + 1;

    CKeyID id = key.GetPubKey().GetID();

    memcpy(out.vchFingerprint, &id, 4);

    out.nChild = _nChild;

    return key.Derive(out.key, out.chaincode, _nChild, chaincode);

}

void CExtKey::SetSeed(std::span<const std::byte> seed)

{

    static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};

    std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);

    CHMAC_SHA512{hashkey, sizeof(hashkey)}.Write(UCharCast(seed.data()), seed.size()).Finalize(vout.data());

    key.Set(vout.data(), vout.data() + 32, true);

    memcpy(chaincode.begin(), vout.data() + 32, 32);

    nDepth = 0;

    nChild = 0;

    memset(vchFingerprint, 0, sizeof(vchFingerprint));

}

CExtPubKey CExtKey::Neuter() const {

    CExtPubKey ret;

    ret.nDepth = nDepth;

    memcpy(ret.vchFingerprint, vchFingerprint, 4);

    ret.nChild = nChild;

    ret.pubkey = key.GetPubKey();

    ret.chaincode = chaincode;

    return ret;

}

void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {

    code[0] = nDepth;

    memcpy(code+1, vchFingerprint, 4);

    WriteBE32(code+5, nChild);

    memcpy(code+9, chaincode.begin(), 32);

    code[41] = 0;

    assert(key.size() == 32);

    memcpy(code+42, key.begin(), 32);

}

void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {

    nDepth = code[0];

    memcpy(vchFingerprint, code+1, 4);

    nChild = ReadBE32(code+5);

    memcpy(chaincode.begin(), code+9, 32);

    key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);

    if ((nDepth == 0 && (nChild != 0 || ReadLE32(vchFingerprint) != 0)) || code[41] != 0) key = CKey();

}

KeyPair::KeyPair(const CKey& key, const uint256* merkle_root)

{

    static_assert(std::tuple_size<KeyType>() == sizeof(secp256k1_keypair));

    MakeKeyPairData();

    auto keypair = reinterpret_cast<secp256k1_keypair*>(m_keypair->data());

    bool success = secp256k1_keypair_create(secp256k1_context_sign, keypair, UCharCast(key.data()));

    if (success && merkle_root) {

        secp256k1_xonly_pubkey pubkey;

        unsigned char pubkey_bytes[32];

        assert(secp256k1_keypair_xonly_pub(secp256k1_context_static, &pubkey, nullptr, keypair));

        assert(secp256k1_xonly_pubkey_serialize(secp256k1_context_static, pubkey_bytes, &pubkey));

        uint256 tweak = XOnlyPubKey(pubkey_bytes).ComputeTapTweakHash(merkle_root->IsNull() ? nullptr : merkle_root);

        success = secp256k1_keypair_xonly_tweak_add(secp256k1_context_static, keypair, tweak.data());

    }

    if (!success) ClearKeyPairData();

}

bool KeyPair::SignSchnorr(const uint256& hash, std::span<unsigned char> sig, const uint256& aux) const

{

    assert(sig.size() == 64);

    if (!IsValid()) return false;

    auto keypair = reinterpret_cast<const secp256k1_keypair*>(m_keypair->data());

    bool ret = secp256k1_schnorrsig_sign32(secp256k1_context_sign, sig.data(), hash.data(), keypair, aux.data());

    if (ret) {

        // Additional verification step to prevent using a potentially corrupted signature

        secp256k1_xonly_pubkey pubkey_verify;

        ret = secp256k1_keypair_xonly_pub(secp256k1_context_static, &pubkey_verify, nullptr, keypair);

        ret &= secp256k1_schnorrsig_verify(secp256k1_context_static, sig.data(), hash.begin(), 32, &pubkey_verify);

    }

    if (!ret) memory_cleanse(sig.data(), sig.size());

    return ret;

}

bool ECC_InitSanityCheck() {

    CKey key = GenerateRandomKey();

    CPubKey pubkey = key.GetPubKey();

    return key.VerifyPubKey(pubkey);

}

/** Initialize the elliptic curve support. May not be called twice without calling ECC_Stop first. */

static void ECC_Start() {

    assert(secp256k1_context_sign == nullptr);

    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_NONE);

    assert(ctx != nullptr);

    {

        // Pass in a random blinding seed to the secp256k1 context.

        std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);

        GetRandBytes(vseed);

        bool ret = secp256k1_context_randomize(ctx, vseed.data());

        assert(ret);

    }

    secp256k1_context_sign = ctx;

}

/** Deinitialize the elliptic curve support. No-op if ECC_Start wasn't called first. */

static void ECC_Stop() {

    secp256k1_context *ctx = secp256k1_context_sign;

    secp256k1_context_sign = nullptr;

    if (ctx) {

        secp256k1_context_destroy(ctx);

    }

}

ECC_Context::ECC_Context()

{

    ECC_Start();

}

ECC_Context::~ECC_Context()

{

    ECC_Stop();

}