using Org.BouncyCastle.Math.Raw; using System; namespace Org.BouncyCastle.Math.EC.Multiplier { public class FixedPointCombMultiplier : AbstractECMultiplier { protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k) { ECCurve curve = p.Curve; int combSize = FixedPointUtilities.GetCombSize(curve); if (k.BitLength > combSize) throw new InvalidOperationException("fixed-point comb doesn't support scalars larger than the curve order"); FixedPointPreCompInfo fixedPointPreCompInfo = FixedPointUtilities.Precompute(p); ECLookupTable lookupTable = fixedPointPreCompInfo.LookupTable; int width = fixedPointPreCompInfo.Width; int num = (combSize + width - 1) / width; int num2 = num * width; uint[] array = Nat.FromBigInteger(num2, k); ECPoint eCPoint = curve.Infinity; for (int i = 1; i <= num; i++) { uint num3 = 0; for (int num4 = num2 - i; num4 >= 0; num4 -= num) { uint num5 = array[num4 >> 5] >> num4; num3 ^= num5 >> 1; num3 <<= 1; num3 ^= num5; } ECPoint b = lookupTable.Lookup((int)num3); eCPoint = eCPoint.TwicePlus(b); } return eCPoint.Add(fixedPointPreCompInfo.Offset); } } }