public void montgomery_reduce_matches_from_bytes_mod_order_wide()
{
var bignum = new byte [64];
// set bignum = x + 2^256x
for (int i = 0; i < 32; i++)
{
bignum[i] = X.Value[i];
bignum[32 + i] = X.Value[i];
}
// x + 2^256x (mod l)
// = 3958878930004874126169954872055634648693766179881526445624823978500314864344
var expected = new Scalar(new byte[]
{
216, 154, 179, 139, 210, 121, 2, 71,
69, 99, 158, 216, 23, 173, 63, 100,
204, 0, 91, 50, 219, 153, 57, 249,
28, 82, 31, 197, 100, 165, 192, 8
});
var reduced = Scalar.from_bytes_mod_order_wide(bignum);
// The reduced scalar should match the expected
Assert.Equal(reduced.Value.ToArray(), expected.Value.ToArray());
// (x + 2^256x) * R
var interim = UnpackedScalar.mul_internal(UnpackedScalar.from_bytes_wide(bignum).Value, Constant.R.Value);
// ((x + 2^256x) * R) / R (mod l)
var montgomery_reduced = UnpackedScalar.montgomery_reduce(interim);
// The Montgomery reduced scalar should match the reduced one, as well as the expected
Assert.Equal(montgomery_reduced.to_bytes(), reduced.unpack().to_bytes());
Assert.Equal(montgomery_reduced.to_bytes(), expected.unpack().to_bytes());
}
public void to_bytes_from_bytes_roundtrips()
{
var unpacked = X.unpack();
var bytes = unpacked.to_bytes();
var should_be_unpacked = UnpackedScalar.from_bytes(bytes);
Assert.Equal(should_be_unpacked.to_bytes(), unpacked.to_bytes());
}
public void montgomery_mul_max()
{
var res = UnpackedScalar.montgomery_mul(X, X);
for (int i = 0; i < 5; i++)
{
Assert.Equal(XX_MONT.Value[i], res.Value[i]);
}
}
public void sub()
{
var res = UnpackedScalar.sub(A, B);
for (int i = 0; i < 5; i++)
{
Assert.Equal(AB.Value[i], res.Value[i]);
}
}
public void mul()
{
var res = UnpackedScalar.mul(X, Y);
for (int i = 0; i < 5; i++)
{
Assert.Equal(XY.Value[i], res.Value[i]);
}
}
public void add()
{
var res = UnpackedScalar.add(A, B);
var zero = UnpackedScalar.zero();
for (int i = 0; i < 5; i++)
{
Assert.Equal(zero.Value[i], res.Value[i]);
}
}
public void from_bytes_wide()
{
var bignum = Enumerable.Repeat((byte)255, 64).ToArray(); // 2^512 - 1
var reduced = UnpackedScalar.from_bytes_wide(bignum);
Console.WriteLine("{0}", reduced);
for (int i = 0; i < 5; i++)
{
Assert.Equal(C.Value[i], reduced.Value[i]);
}
}
