diff options
Diffstat (limited to 'crypto/src/math/ec/multiplier/FixedPointCombMultiplier.cs')
| -rw-r--r-- | crypto/src/math/ec/multiplier/FixedPointCombMultiplier.cs | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/crypto/src/math/ec/multiplier/FixedPointCombMultiplier.cs b/crypto/src/math/ec/multiplier/FixedPointCombMultiplier.cs index 05bb4000b..adaedb809 100644 --- a/crypto/src/math/ec/multiplier/FixedPointCombMultiplier.cs +++ b/crypto/src/math/ec/multiplier/FixedPointCombMultiplier.cs @@ -1,5 +1,7 @@ using System; +using Org.BouncyCastle.Math.Raw; + namespace Org.BouncyCastle.Math.EC.Multiplier { public class FixedPointCombMultiplier @@ -21,36 +23,37 @@ namespace Org.BouncyCastle.Math.EC.Multiplier throw new InvalidOperationException("fixed-point comb doesn't support scalars larger than the curve order"); } - int minWidth = GetWidthForCombSize(size); - - FixedPointPreCompInfo info = FixedPointUtilities.Precompute(p, minWidth); - ECPoint[] lookupTable = info.PreComp; + FixedPointPreCompInfo info = FixedPointUtilities.Precompute(p); + ECLookupTable lookupTable = info.LookupTable; int width = info.Width; int d = (size + width - 1) / width; ECPoint R = c.Infinity; - int top = d * width - 1; + int fullComb = d * width; + uint[] K = Nat.FromBigInteger(fullComb, k); + + int top = fullComb - 1; for (int i = 0; i < d; ++i) { - int index = 0; + int secretIndex = 0; for (int j = top - i; j >= 0; j -= d) { - index <<= 1; - if (k.TestBit(j)) - { - index |= 1; - } + secretIndex <<= 1; + secretIndex |= (int)Nat.GetBit(K, j); } - R = R.TwicePlus(lookupTable[index]); + ECPoint add = lookupTable.Lookup(secretIndex); + + R = R.TwicePlus(add); } return R.Add(info.Offset); } + [Obsolete("Is no longer used; remove any overrides in subclasses.")] protected virtual int GetWidthForCombSize(int combSize) { return combSize > 257 ? 6 : 5; |