Method Sign

src/key.cpp:223–249

}

bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool grind, uint32_t test_case) const {
    if (!fValid)
        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(), 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(), begin(), secp256k1_nonce_function_rfc6979, extra_entropy);
    }
    assert(ret);
    secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, 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, begin());
    assert(ret);
    ret = secp256k1_ecdsa_verify(GetVerifyContext(), &sig, hash.begin(), &pk);
    assert(ret);
    return true;
}

bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
    if (pubkey.IsCompressed() != fCompressed) {