static Context CreateInstance()
{
var gen = new ECMultGenContext();
gen.Blind(RandomUtils.GetBytes(32));
return(new Context(new ECMultContext(), gen));
}
public uint256 BlindMessage(uint256 message, PubKey rpubkey, PubKey signerPubKey)
{
var ctx = new ECMultGenContext();
int overflow;
Span <byte> tmp = stackalloc byte[32];
if (!Context.Instance.TryCreatePubKey(signerPubKey.ToBytes(), out var signerECPubkey))
{
throw new FormatException("Invalid signer pubkey.");
}
if (!Context.Instance.TryCreatePubKey(rpubkey.ToBytes(), out var rECPubKey))
{
throw new FormatException("Invalid r pubkey.");
}
var P = signerECPubkey.Q;
var R = rECPubKey.Q.ToGroupElementJacobian();
var t = FE.Zero;
retry:
RandomUtils.GetBytes(tmp);
_v = new Scalar(tmp, out overflow);
if (overflow != 0 || _v.IsZero)
{
goto retry;
}
RandomUtils.GetBytes(tmp);
_w = new Scalar(tmp, out overflow);
if (overflow != 0 || _v.IsZero)
{
goto retry;
}
var A1 = ctx.MultGen(_v);
var A2 = _w * P;
var A = R.AddVariable(A1, out _).AddVariable(A2, out _).ToGroupElement();
t = A.x.Normalize();
if (t.IsZero)
{
goto retry;
}
using (var sha = new SHA256())
{
message.ToBytes(tmp, false);
sha.Write(tmp);
t.WriteToSpan(tmp);
sha.Write(tmp);
sha.GetHash(tmp);
}
_c = new Scalar(tmp, out overflow);
if (overflow != 0 || _c.IsZero)
{
goto retry;
}
var cp = _c.Add(_w.Negate(), out overflow); // this is sent to the signer (blinded message)
if (cp.IsZero || overflow != 0)
{
goto retry;
}
cp.WriteToSpan(tmp);
return(new uint256(tmp));
}
