public static void crypto_sign_prehashed(
byte[] sig,
byte[] m, int mlen,
byte[] sk,
byte[] pk
)
{
byte[] r, hram;
GroupElementP3 R;
var hasher = new Sha512();
{
hasher.Init();
hasher.Update(sk, 32, 32);
hasher.Update(m, 0, mlen);
r = hasher.Finalize();
ScalarOperations.sc_reduce(r);
GroupOperations.ge_scalarmult_base(out R, r, 0);
GroupOperations.ge_p3_tobytes(sig, 0, ref R);
hasher.Init();
hasher.Update(sig, 0, 32);
hasher.Update(pk, 0, 32);
hasher.Update(m, 0, mlen);
hram = hasher.Finalize();
ScalarOperations.sc_reduce(hram);
var s = new byte[32]; //todo: remove allocation
Array.Copy(sig, 32, s, 0, 32);
ScalarOperations.sc_muladd(s, hram, sk, r);
Array.Copy(s, 0, sig, 32, 32);
CryptoBytes.Wipe(s);
}
}
// Original crypto_sign_open, for reference only
/*public static int crypto_sign_open(
* byte[] m, out int mlen,
* byte[] sm, int smlen,
* byte[] pk)
* {
* byte[] h = new byte[64];
* byte[] checkr = new byte[32];
* GroupElementP3 A;
* GroupElementP2 R;
* int i;
*
* mlen = -1;
* if (smlen < 64) return -1;
* if ((sm[63] & 224) != 0) return -1;
* if (GroupOperations.ge_frombytes_negate_vartime(out A, pk, 0) != 0) return -1;
*
* for (i = 0; i < smlen; ++i) m[i] = sm[i];
* for (i = 0; i < 32; ++i) m[32 + i] = pk[i];
* Sha512BclWrapper.crypto_hash_sha512(h, m, 0, smlen);
* ScalarOperations.sc_reduce(h);
*
* var sm32 = new byte[32];
* Array.Copy(sm, 32, sm32, 0, 32);
* GroupOperations.ge_double_scalarmult_vartime(out R, h, ref A, sm32);
* GroupOperations.ge_tobytes(checkr, 0, ref R);
* if (Helpers.crypto_verify_32(checkr, sm) != 0)
* {
* for (i = 0; i < smlen; ++i)
* m[i] = 0;
* return -1;
* }
*
* for (i = 0; i < smlen - 64; ++i)
* m[i] = sm[64 + i];
* for (i = smlen - 64; i < smlen; ++i)
* m[i] = 0;
* mlen = smlen - 64;
* return 0;
* }*/
public static bool crypto_sign_verify(
byte[] sig, int sigoffset,
byte[] m, int moffset, int mlen,
byte[] pk, int pkoffset)
{
byte[] h;
byte[] checkr = new byte[32];
GroupElementP3 A;
GroupElementP2 R;
if ((sig[sigoffset + 63] & 224) != 0)
{
return(false);
}
if (GroupOperations.ge_frombytes_negate_vartime(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);
h = hasher.Finalize();
ScalarOperations.sc_reduce(h);
var sm32 = new byte[32];//todo: remove allocation
Array.Copy(sig, sigoffset + 32, sm32, 0, 32);
GroupOperations.ge_double_scalarmult_vartime(out R, h, ref A, sm32);
GroupOperations.ge_tobytes(checkr, 0, ref R);
var result = CryptoBytes.ConstantTimeEquals(checkr, 0, sig, sigoffset, 32);
CryptoBytes.Wipe(h);
CryptoBytes.Wipe(checkr);
return(result);
}
public static void crypto_sign(
byte[] sig, int sigoffset,
byte[] m, int moffset, int mlen,
byte[] sk, int skoffset)
{
byte[] az, r, hram;
GroupElementP3 R;
var hasher = new Sha512();
{
hasher.Update(sk, skoffset, 32);
az = hasher.Finalize();
ScalarOperations.sc_clamp(az, 0);
hasher.Init();
hasher.Update(az, 32, 32);
hasher.Update(m, moffset, mlen);
r = hasher.Finalize();
ScalarOperations.sc_reduce(r);
GroupOperations.ge_scalarmult_base(out R, r, 0);
GroupOperations.ge_p3_tobytes(sig, sigoffset, ref R);
hasher.Init();
hasher.Update(sig, sigoffset, 32);
hasher.Update(sk, skoffset + 32, 32);
hasher.Update(m, moffset, mlen);
hram = hasher.Finalize();
ScalarOperations.sc_reduce(hram);
var s = new byte[32]; //todo: remove allocation
Array.Copy(sig, sigoffset + 32, s, 0, 32);
ScalarOperations.sc_muladd(s, hram, az, r);
Array.Copy(s, 0, sig, sigoffset + 32, 32);
CryptoBytes.Wipe(s);
}
}