Function NegateSignatureS

src/test/script_tests.cpp:168–206

}

void static NegateSignatureS(std::vector<unsigned char>& vchSig) {
    // Parse the signature.
    std::vector<unsigned char> r, s;
    r = std::vector<unsigned char>(vchSig.begin() + 4, vchSig.begin() + 4 + vchSig[3]);
    s = std::vector<unsigned char>(vchSig.begin() + 6 + vchSig[3], vchSig.begin() + 6 + vchSig[3] + vchSig[5 + vchSig[3]]);

    // Really ugly to implement mod-n negation here, but it would be feature creep to expose such functionality from libsecp256k1.
    static const unsigned char order[33] = {
        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
    };
    while (s.size() < 33) {
        s.insert(s.begin(), 0x00);
    }
    int carry = 0;
    for (int p = 32; p >= 1; p--) {
        int n = (int)order[p] - s[p] - carry;
        s[p] = (n + 256) & 0xFF;
        carry = (n < 0);
    }
    assert(carry == 0);
    if (s.size() > 1 && s[0] == 0 && s[1] < 0x80) {
        s.erase(s.begin());
    }

    // Reconstruct the signature.
    vchSig.clear();
    vchSig.push_back(0x30);
    vchSig.push_back(4 + r.size() + s.size());
    vchSig.push_back(0x02);
    vchSig.push_back(r.size());
    vchSig.insert(vchSig.end(), r.begin(), r.end());
    vchSig.push_back(0x02);
    vchSig.push_back(s.size());
    vchSig.insert(vchSig.end(), s.begin(), s.end());
}

namespace
{