From 17397bac85c830365ee6968fb09373165c6f1dc1 Mon Sep 17 00:00:00 2001 From: Peter Dettman Date: Sun, 2 Feb 2014 14:49:51 +0700 Subject: Minor optimization for secp521r1 point doubling --- crypto/src/math/ec/custom/sec/SecP521R1Field.cs | 12 ++++++++++++ crypto/src/math/ec/custom/sec/SecP521R1Point.cs | 9 ++++----- 2 files changed, 16 insertions(+), 5 deletions(-) (limited to 'crypto/src/math/ec/custom') diff --git a/crypto/src/math/ec/custom/sec/SecP521R1Field.cs b/crypto/src/math/ec/custom/sec/SecP521R1Field.cs index 43f012b8b..f39a0daa6 100644 --- a/crypto/src/math/ec/custom/sec/SecP521R1Field.cs +++ b/crypto/src/math/ec/custom/sec/SecP521R1Field.cs @@ -85,6 +85,18 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec z[16] = c; } + public static void Reduce23(uint[] z) + { + uint z16 = z[16]; + uint c = Nat.AddWord(16, z16 >> 9, z) + (z16 & P16); + if (c > P16 || (c == P16 && Nat.Eq(16, z, P))) + { + c += Nat.Inc(16, z, 0); + c &= P16; + } + z[16] = c; + } + public static void Square(uint[] x, uint[] z) { uint[] tt = Nat.Create(34); diff --git a/crypto/src/math/ec/custom/sec/SecP521R1Point.cs b/crypto/src/math/ec/custom/sec/SecP521R1Point.cs index 5da71f078..2e3a7eccb 100644 --- a/crypto/src/math/ec/custom/sec/SecP521R1Point.cs +++ b/crypto/src/math/ec/custom/sec/SecP521R1Point.cs @@ -216,12 +216,11 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec uint[] S = Y1Squared; SecP521R1Field.Multiply(Y1Squared, X1.x, S); - SecP521R1Field.Twice(S, S); - SecP521R1Field.Twice(S, S); + Nat.ShiftUpBits(17, S, 2, 0); + SecP521R1Field.Reduce23(S); - SecP521R1Field.Twice(T, t1); - SecP521R1Field.Twice(t1, t1); - SecP521R1Field.Twice(t1, t1); + Nat.ShiftUpBits(17, T, 3, 0, t1); + SecP521R1Field.Reduce23(t1); SecP521R1FieldElement X3 = new SecP521R1FieldElement(T); SecP521R1Field.Square(M, X3.x); -- cgit 1.4.1