public static void CryptoSign(
byte[] sig, int sigoffset,
byte[] m, int moffset, int mlen,
byte[] sk, int skoffset)
{
var hasher = new Sha512();
{
hasher.Update(sk, skoffset, 32);
var az = hasher.Finalize();
ScalarOperations.Clamp(az, 0);
hasher.Init();
hasher.Update(az, 32, 32);
hasher.Update(m, moffset, mlen);
var r = hasher.Finalize();
ScalarOperations.Reduce(r);
GroupElementP3 R;
GroupOperations.ScalarMultBase(out R, r, 0);
GroupOperations.P3ToBytes(sig, sigoffset, ref R);
hasher.Init();
hasher.Update(sig, sigoffset, 32);
hasher.Update(sk, skoffset + 32, 32);
hasher.Update(m, moffset, mlen);
var hram = hasher.Finalize();
ScalarOperations.Reduce(hram);
var s = new byte[32];
Array.Copy(sig, sigoffset + 32, s, 0, 32);
ScalarOperations.MulAdd(s, hram, az, r);
Array.Copy(s, 0, sig, sigoffset + 32, 32);
CryptoBytes.Wipe(s);
}
}
public static bool CryptoSignVerify(
byte[] sig, int sigoffset,
byte[] m, int moffset, int mlen,
byte[] pk, int pkoffset)
{
var checker = new byte[32];
GroupElementP3 A;
GroupElementP2 R;
if ((sig[sigoffset + 63] & 224) != 0)
{
return(false);
}
if (GroupOperations.FromBytes(out A, pk, pkoffset) != 0)
{
return(false);
}
var hasher = new Sha512();
hasher.Update(sig, sigoffset, 32);
hasher.Update(pk, pkoffset, 32);
hasher.Update(m, moffset, mlen);
var h = hasher.Finalize();
ScalarOperations.Reduce(h);
var sm32 = new byte[32];
Array.Copy(sig, sigoffset + 32, sm32, 0, 32);
GroupOperations.DoubleScalarMult(out R, h, ref A, sm32);
GroupOperations.ToBytes(checker, 0, ref R);
var result = CryptoBytes.ConstantTimeEquals(checker, 0, sig, sigoffset, 32);
CryptoBytes.Wipe(h);
CryptoBytes.Wipe(checker);
return(result);
}
