Signature Secp256k1PP::sign(Secret const& _key, h256 const& _hash)
{
// assumption made by signing alogrithm
assert(m_q == m_qs);
Signature sig;
Integer k(kdf(_key, _hash).data(), 32);
if (k == 0)
BOOST_THROW_EXCEPTION(InvalidState());
k = 1 + (k % (m_qs - 1));
ECP::Point rp;
Integer r;
{
Guard l(x_params);
rp = m_params.ExponentiateBase(k);
r = m_params.ConvertElementToInteger(rp);
}
sig[64] = 0;
// sig[64] = (r >= m_q) ? 2 : 0;
Integer kInv = k.InverseMod(m_q);
Integer z(_hash.asBytes().data(), 32);
Integer s = (kInv * (Integer(_key.data(), 32) * r + z)) % m_q;
if (r == 0 || s == 0)
BOOST_THROW_EXCEPTION(InvalidState());
// if (s > m_qs)
// {
// s = m_q - s;
// if (sig[64])
// sig[64] ^= 1;
// }
sig[64] |= rp.y.IsOdd() ? 1 : 0;
r.Encode(sig.data(), 32);
s.Encode(sig.data() + 32, 32);
return sig;
}
