WTauNafMultiplier
using Org.BouncyCastle.Math.EC.Abc;
using System;
namespace Org.BouncyCastle.Math.EC.Multiplier
{
public class WTauNafMultiplier : AbstractECMultiplier
{
private class WTauNafCallback : IPreCompCallback
{
private readonly AbstractF2mPoint m_p;
private readonly sbyte m_a;
internal WTauNafCallback(AbstractF2mPoint p, sbyte a)
{
m_p = p;
m_a = a;
}
public PreCompInfo Precompute(PreCompInfo existing)
{
if (existing is WTauNafPreCompInfo)
return existing;
return new WTauNafPreCompInfo {
PreComp = Tnaf.GetPreComp(m_p, m_a)
};
}
}
internal static readonly string PRECOMP_NAME = "bc_wtnaf";
protected override ECPoint MultiplyPositive(ECPoint point, BigInteger k)
{
AbstractF2mPoint abstractF2mPoint = point as AbstractF2mPoint;
if (abstractF2mPoint == null)
throw new ArgumentException("Only AbstractF2mPoint can be used in WTauNafMultiplier");
AbstractF2mCurve obj = (AbstractF2mCurve)abstractF2mPoint.Curve;
sbyte b = (sbyte)obj.A.ToBigInteger().IntValue;
sbyte mu = Tnaf.GetMu(b);
ZTauElement lambda = Tnaf.PartModReduction(obj, k, b, mu, 10);
return MultiplyWTnaf(abstractF2mPoint, lambda, b, mu);
}
private AbstractF2mPoint MultiplyWTnaf(AbstractF2mPoint p, ZTauElement lambda, sbyte a, sbyte mu)
{
ZTauElement[] alpha = (a == 0) ? Tnaf.Alpha0 : Tnaf.Alpha1;
BigInteger tw = Tnaf.GetTw(mu, 4);
sbyte[] u = Tnaf.TauAdicWNaf(mu, lambda, 4, tw.IntValue, alpha);
return MultiplyFromWTnaf(p, u);
}
private static AbstractF2mPoint MultiplyFromWTnaf(AbstractF2mPoint p, sbyte[] u)
{
AbstractF2mCurve obj = (AbstractF2mCurve)p.Curve;
sbyte a = (sbyte)obj.A.ToBigInteger().IntValue;
AbstractF2mPoint[] preComp = ((WTauNafPreCompInfo)obj.Precompute(callback: new WTauNafCallback(p, a), point: p, name: PRECOMP_NAME)).PreComp;
AbstractF2mPoint[] array = new AbstractF2mPoint[preComp.Length];
for (int i = 0; i < preComp.Length; i++) {
array[i] = (AbstractF2mPoint)preComp[i].Negate();
}
AbstractF2mPoint abstractF2mPoint = (AbstractF2mPoint)p.Curve.Infinity;
int num = 0;
for (int num2 = u.Length - 1; num2 >= 0; num2--) {
num++;
int num3 = u[num2];
if (num3 != 0) {
abstractF2mPoint = abstractF2mPoint.TauPow(num);
num = 0;
ECPoint b = (num3 > 0) ? preComp[num3 >> 1] : array[-num3 >> 1];
abstractF2mPoint = (AbstractF2mPoint)abstractF2mPoint.Add(b);
}
}
if (num > 0)
abstractF2mPoint = abstractF2mPoint.TauPow(num);
return abstractF2mPoint;
}
}
}