public EdwardsPoint Mul(Scalar sclr)
{
var a = sclr.ToRadix16();
var P = EdwardsPoint.Identity();
for (var i = 0; i < 64; i++)
{
if (i % 2 == 1)
{
var s1 = lt[i / 2].Select(a[i]);
var s2 = P.Add(s1);
var s3 = s2.ToExtended();
P = s3;
}
}
P = P.MulByPow2(4);
for (var i = 0; i < 64; i++)
{
if (i % 2 == 0)
{
P = P.Add(lt[i / 2].Select(a[i])).ToExtended();
}
}
return(P);
}
public LookupTable(EdwardsPoint ep)
{
_ep = ep;
affineNielsPoints = new AffineNielsPoint[8];
affineNielsPoints[0] = ep.ToAffineNiels();
for (var j = 0; j < 7; j++)
{
affineNielsPoints[j + 1] = ep.Add(affineNielsPoints[j]).ToExtended().ToAffineNiels();
}
}
public bool Equals(EdwardsPoint a)
{
bool result = true;
for (var i = 0; i < 5; i++)
{
result &= X._data[i] == a.X._data[i] &&
Y._data[i] == a.Y._data[i] &&
Z._data[i] == a.Z._data[i] &&
T._data[i] == a.T._data[i];
}
return(result);
}
internal static EdwardsPoint Double(EdwardsPoint point)
{
return(point.ToProjective().Double().ToExtended());
}
public EdwardsPoint Add(EdwardsPoint other)
{
return(Add(other.ToProjectiveNiels()).ToExtended());
}
public static LookupTable From(EdwardsPoint ep)
{
return(new LookupTable(ep));
}
/// Compute \\(aA + bB\\) in variable time, where \\(B\\) is the
/// Ristretto basepoint.
public static EdwardsPoint VartimeDoubleScalarMulBasepoint(Scalar a, EdwardsPoint A, Scalar b)
{
var aNaf = a.NonAdjacentForm(5);
var bNaf = b.NonAdjacentForm(8);
int i = 0;
/// Find starting index
for (var ind = 255; ind >= 0; ind--)
{
i = ind;
if (aNaf[i] != 0 || bNaf[i] != 0)
{
break;
}
}
var tableA = NafLookupTable.FromEdwardsPoint(A);
var tableB = Consts.AFFINE_ODD_MULTIPLES_OF_BASEPOINT;
var r = ProjectivePoint.Identity();
while (i >= 0)
{
var t = r.Double();
if (aNaf[i] > 0)
{
var t1 = t.ToExtended();
var i1 = Math.Abs((sbyte)(-1 * aNaf[i]) / 2);
var t2 = tableA.Pnp[i1];
t = t1.Add(t2);
}
else if (aNaf[i] < 0)
{
var t1 = t.ToExtended();
var i1 = Math.Abs((sbyte)(-1 * aNaf[i]) / 2);
var t2 = tableA.Pnp[i1];
t = t1.Sub(t2);
}
if (bNaf[i] > 0)
{
var t1 = t.ToExtended();
var i1 = Math.Abs((sbyte)(-1 * bNaf[i]) / 2);
var t2 = tableB.affineNielsPoints[i1];
t = t1.Add(t2);
}
else if (bNaf[i] < 0)
{
var t1 = t.ToExtended();
var i1 = Math.Abs((sbyte)(-1 * bNaf[i]) / 2);
var t2 = tableB.affineNielsPoints[i1];
t = t1.Sub(t2);
}
r = t.ToProjective();
i--;
}
return(r.ToExtended());
}
public RistrettoPoint(EdwardsPoint ep)
{
Ep = ep;
}
