using Org.BouncyCastle.Math.EC.Multiplier; namespace Org.BouncyCastle.Math.EC.Endo { public abstract class EndoUtilities { private class MapPointCallback : IPreCompCallback { private readonly ECEndomorphism m_endomorphism; private readonly ECPoint m_point; internal MapPointCallback(ECEndomorphism endomorphism, ECPoint point) { m_endomorphism = endomorphism; m_point = point; } public PreCompInfo Precompute(PreCompInfo existing) { EndoPreCompInfo endoPreCompInfo = existing as EndoPreCompInfo; if (CheckExisting(endoPreCompInfo, m_endomorphism)) return endoPreCompInfo; ECPoint mappedPoint = m_endomorphism.PointMap.Map(m_point); return new EndoPreCompInfo { Endomorphism = m_endomorphism, MappedPoint = mappedPoint }; } private bool CheckExisting(EndoPreCompInfo existingEndo, ECEndomorphism endomorphism) { if (existingEndo != null && existingEndo.Endomorphism == endomorphism) return existingEndo.MappedPoint != null; return false; } } public static readonly string PRECOMP_NAME = "bc_endo"; public static BigInteger[] DecomposeScalar(ScalarSplitParameters p, BigInteger k) { int bits = p.Bits; BigInteger bigInteger = CalculateB(k, p.G1, bits); BigInteger bigInteger2 = CalculateB(k, p.G2, bits); BigInteger bigInteger3 = k.Subtract(bigInteger.Multiply(p.V1A).Add(bigInteger2.Multiply(p.V2A))); BigInteger bigInteger4 = bigInteger.Multiply(p.V1B).Add(bigInteger2.Multiply(p.V2B)).Negate(); return new BigInteger[2] { bigInteger3, bigInteger4 }; } public static ECPoint MapPoint(ECEndomorphism endomorphism, ECPoint p) { return ((EndoPreCompInfo)p.Curve.Precompute(p, PRECOMP_NAME, new MapPointCallback(endomorphism, p))).MappedPoint; } private static BigInteger CalculateB(BigInteger k, BigInteger g, int t) { bool num = g.SignValue < 0; BigInteger bigInteger = k.Multiply(g.Abs()); bool num2 = bigInteger.TestBit(t - 1); bigInteger = bigInteger.ShiftRight(t); if (num2) bigInteger = bigInteger.Add(BigInteger.One); if (!num) return bigInteger; return bigInteger.Negate(); } } }