diff options
| author | Peter Dettman <peter.dettman@bouncycastle.org> | 2014-01-24 10:40:37 +0700 |
|---|---|---|
| committer | Peter Dettman <peter.dettman@bouncycastle.org> | 2014-01-24 10:40:37 +0700 |
| commit | d64985881f898bc4779d31cf618e1a04b1cece6f (patch) | |
| tree | 75e6ef17b0ccf628945ad1211ac0362f0893df56 /crypto/src/math/ec/Mod.cs | |
| parent | Move method (diff) | |
| download | BouncyCastle.NET-ed25519-d64985881f898bc4779d31cf618e1a04b1cece6f.tar.xz | |
Track uvLen to reduce shifting for small operands
Diffstat (limited to '')
| -rw-r--r-- | crypto/src/math/ec/Mod.cs | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/crypto/src/math/ec/Mod.cs b/crypto/src/math/ec/Mod.cs index 57f75ed12..465aa5e41 100644 --- a/crypto/src/math/ec/Mod.cs +++ b/crypto/src/math/ec/Mod.cs @@ -21,7 +21,7 @@ namespace Org.BouncyCastle.Math.EC if ((u[0] & 1) == 0) { - InversionStep(p, u, a); + InversionStep(p, u, len, a); } if (Nat.IsOne(len, u)) { @@ -32,15 +32,22 @@ namespace Org.BouncyCastle.Math.EC uint[] v = Nat.Copy(len, p); uint[] b = Nat.Create(len); + int uvLen = len; + for (;;) { + while (u[uvLen - 1] == 0 && v[uvLen - 1] == 0) + { + --uvLen; + } + if (Nat.Gte(len, u, v)) { Subtract(p, a, b, a); Nat.Sub(len, u, v, u); if ((u[0] & 1) == 0) { - InversionStep(p, u, a); + InversionStep(p, u, uvLen, a); } if (Nat.IsOne(len, u)) { @@ -54,7 +61,7 @@ namespace Org.BouncyCastle.Math.EC Nat.Sub(len, v, u, v); if ((v[0] & 1) == 0) { - InversionStep(p, v, b); + InversionStep(p, v, uvLen, b); } if (Nat.IsOne(len, v)) { @@ -75,21 +82,23 @@ namespace Org.BouncyCastle.Math.EC } } - private static void InversionStep(uint[] p, uint[] u, uint[] x) + private static void InversionStep(uint[] p, uint[] u, int uLen, uint[] x) { int len = p.Length; int count = 0; while (u[0] == 0) { - Nat.ShiftDownWord(u, len, 0); + Nat.ShiftDownWord(u, uLen, 0); count += 32; } - int zeroes = GetTrailingZeroes(u[0]); - if (zeroes > 0) { - Nat.ShiftDownBits(u, len, zeroes, 0); - count += zeroes; + int zeroes = GetTrailingZeroes(u[0]); + if (zeroes > 0) + { + Nat.ShiftDownBits(u, uLen, zeroes, 0); + count += zeroes; + } } for (int i = 0; i < count; ++i) |