public override Boolean Verify(byte[] publicKey, byte[] message, byte[] signature, byte[] rgbContext = null)
{
EdDSAPoint A = DecodePoint(publicKey);
byte[] r = new byte[signature.Length / 2];
Array.Copy(signature, r, r.Length);
EdDSAPoint R = DecodePoint(r);
byte[] s = new byte[signature.Length / 2];
Array.Copy(signature, r.Length, s, 0, r.Length);
Array.Reverse(s);
BigInteger S = new BigInteger(1, s);
message = PreHash(message);
ShakeDigest sha256 = new ShakeDigest(256);
byte[] rgbDom = Dom(rgbContext);
sha256.BlockUpdate(rgbDom, 0, rgbDom.Length);
sha256.BlockUpdate(r, 0, r.Length);
sha256.BlockUpdate(publicKey, 0, publicKey.Length);
sha256.BlockUpdate(message, 0, message.Length);
byte[] h = new byte[114];
sha256.DoFinal(h, 0, 114);
Array.Reverse(h);
BigInteger k = new BigInteger(1, h).Mod(EdDSAPoint448.L);
EdDSAPoint left = EdDSAPoint448.B.MultipleByScalar(S).Normalize();
EdDSAPoint right = EdDSAPoint448.Add((EdDSAPoint448)R, (EdDSAPoint448)A.MultipleByScalar(k)).Normalize();
return(left.equal(right));
}
static public EdDSAPoint448 Add(EdDSAPoint448 p1, EdDSAPoint448 p2)
{
BigInteger A = p1.Z.Multiply(p2.Z).Mod(p);
BigInteger B = A.Square().Mod(p);
BigInteger C = p1.X.Multiply(p2.X).Mod(p);
BigInteger D = p1.Y.Multiply(p2.Y).Mod(p);
BigInteger E = d.Multiply(C).Mod(p).Multiply(D).Mod(p);
BigInteger F = B.Subtract(E).Mod(p);
BigInteger G = B.Add(E).Mod(p);
BigInteger H = (p1.X.Add(p1.Y)).Mod(p).Multiply(p2.X.Add(p2.Y).Mod(p)).Mod(p);
BigInteger X3 = A.Multiply(F).Mod(p).Multiply(H.Subtract(C).Mod(p).Subtract(D).Mod(p)).Mod(p);
BigInteger Y3 = A.Multiply(G).Mod(p).Multiply(D.Subtract(C).Mod(p)).Mod(p);
BigInteger Z3 = F.Multiply(G).Mod(p);
return(new EdDSAPoint448(X3, Y3, Z3));
}
public override EdDSAPoint MultipleByScalar(BigInteger k)
{
int i;
EdDSAPoint448 result = new EdDSAPoint448(zero, one, one);
EdDSAPoint448 pNext = this;
for (i = 0; i < k.BitLength; i++)
{
if (k.TestBit(i))
{
result = Add(pNext, result);
}
pNext = pNext.Double();
}
return(result.Normalize());
}
EdDSAPoint448 Double()
{
EdDSAPoint tmp = new EdDSAPoint448(zero, one);
BigInteger C = this.X.Square().Mod(p);
BigInteger D = this.Y.Square().Mod(p);
BigInteger H = this.Z.Square().Mod(p);
BigInteger E = C.Add(D).Mod(p);
BigInteger B = this.X.Add(this.Y).Mod(p).Square().Mod(p);
BigInteger J = E.Subtract(H.Add(H).Mod(p)).Mod(p);
BigInteger X = B.Subtract(E).Mod(p).Multiply(J).Mod(p);
BigInteger Y = E.Multiply(C.Subtract(D).Mod(p)).Mod(p);
BigInteger Z = E.Multiply(J).Mod(p);
return(new EdDSAPoint448(X, Y, Z));
// return Add(this, this);
}
public override EdDSAPoint GetPublic(byte[] privateKey)
{
if (privateKey.Length != 57)
{
throw new CoseException("Invalid private key");
}
ShakeDigest shake = new ShakeDigest(256);
byte[] h = new byte[114];
shake.BlockUpdate(privateKey, 0, privateKey.Length);
shake.DoFinal(h, 0, 114);
Array.Resize(ref h, 57);
h[0] &= 0xfc; // Clear lowest 2 bits
h[56] = 0; // Clear the highest byte
h[55] |= 0x80; // Set the highest bit
Array.Reverse(h);
BigInteger a = new BigInteger(1, h);
EdDSAPoint448 publicKey = (EdDSAPoint448)EdDSAPoint448.B.MultipleByScalar(a);
return(publicKey);
}
