diff options
Diffstat (limited to 'crypto/src/math/ec/abc/Tnaf.cs')
| -rw-r--r-- | crypto/src/math/ec/abc/Tnaf.cs | 210 |
1 files changed, 98 insertions, 112 deletions
diff --git a/crypto/src/math/ec/abc/Tnaf.cs b/crypto/src/math/ec/abc/Tnaf.cs index b6e792aa4..cd3e90f46 100644 --- a/crypto/src/math/ec/abc/Tnaf.cs +++ b/crypto/src/math/ec/abc/Tnaf.cs @@ -1,5 +1,7 @@ using System; +using Org.BouncyCastle.Math.EC.Multiplier; + namespace Org.BouncyCastle.Math.EC.Abc { /** @@ -16,6 +18,8 @@ namespace Org.BouncyCastle.Math.EC.Abc private static readonly BigInteger MinusThree = BigInteger.Three.Negate(); private static readonly BigInteger Four = BigInteger.ValueOf(4); + private static readonly string PRECOMP_NAME = "bc_tnaf_partmod"; + /** * The window width of WTNAF. The standard value of 4 is slightly less * than optimal for running time, but keeps space requirements for @@ -29,11 +33,6 @@ namespace Org.BouncyCastle.Math.EC.Abc public const sbyte Width = 4; /** - * 2<sup>4</sup> - */ - public const sbyte Pow2Width = 16; - - /** * The <code>α<sub>u</sub></code>'s for <code>a=0</code> as an array * of <code>ZTauElement</code>s. */ @@ -449,13 +448,10 @@ namespace Org.BouncyCastle.Math.EC.Abc */ public static BigInteger[] GetLucas(sbyte mu, int k, bool doV) { - if (!(mu == 1 || mu == -1)) + if (!(mu == 1 || mu == -1)) throw new ArgumentException("mu must be 1 or -1"); - BigInteger u0; - BigInteger u1; - BigInteger u2; - + BigInteger u0, u1, u2; if (doV) { u0 = BigInteger.Two; @@ -470,26 +466,18 @@ namespace Org.BouncyCastle.Math.EC.Abc for (int i = 1; i < k; i++) { // u2 = mu*u1 - 2*u0; - BigInteger s = null; - if (mu == 1) + BigInteger s = u1; + if (mu < 0) { - s = u1; + s = s.Negate(); } - else - { - // mu == -1 - s = u1.Negate(); - } - + u2 = s.Subtract(u0.ShiftLeft(1)); u0 = u1; u1 = u2; - // System.out.println(i + ": " + u2); - // System.out.println(); } - BigInteger[] retVal = {u0, u1}; - return retVal; + return new BigInteger[]{ u0, u1 }; } /** @@ -520,11 +508,7 @@ namespace Org.BouncyCastle.Math.EC.Abc BigInteger[] us = GetLucas(mu, w, false); BigInteger twoToW = BigInteger.Zero.SetBit(w); BigInteger u1invert = us[1].ModInverse(twoToW); - BigInteger tw; - tw = BigInteger.Two.Multiply(us[0]).Multiply(u1invert).Mod(twoToW); - //System.out.println("mu = " + mu); - //System.out.println("tw = " + tw); - return tw; + return us[0].ShiftLeft(1).Multiply(u1invert).Mod(twoToW); } } @@ -541,23 +525,7 @@ namespace Org.BouncyCastle.Math.EC.Abc if (!curve.IsKoblitz) throw new ArgumentException("si is defined for Koblitz curves only"); - int m = curve.FieldSize; - int a = curve.A.ToBigInteger().IntValue; - sbyte mu = GetMu(a); - int shifts = GetShiftsForCofactor(curve.Cofactor); - int index = m + 3 - a; - BigInteger[] ui = GetLucas(mu, index, false); - - if (mu == 1) - { - ui[0] = ui[0].Negate(); - ui[1] = ui[1].Negate(); - } - - BigInteger dividend0 = BigInteger.One.Add(ui[1]).ShiftRight(shifts); - BigInteger dividend1 = BigInteger.One.Add(ui[0]).ShiftRight(shifts).Negate(); - - return new BigInteger[] { dividend0, dividend1 }; + return GetSi(curve.FieldSize, curve.A.ToBigInteger().IntValue, curve.Cofactor); } public static BigInteger[] GetSi(int fieldSize, int curveA, BigInteger cofactor) @@ -605,38 +573,39 @@ namespace Org.BouncyCastle.Math.EC.Abc * modular reduction. * @return <code>ρ := k partmod (τ<sup>m</sup> - 1)/(τ - 1)</code> */ - public static ZTauElement PartModReduction(BigInteger k, int m, sbyte a, - BigInteger[] s, sbyte mu, sbyte c) + public static ZTauElement PartModReduction(AbstractF2mCurve curve, BigInteger k, sbyte a, sbyte mu, sbyte c) { + PartModPreCompCallback callback = new PartModPreCompCallback(curve, mu, true); + PartModPreCompInfo preCompInfo = (PartModPreCompInfo)curve.Precompute(PRECOMP_NAME, callback); + + BigInteger vm = preCompInfo.Lucas; + BigInteger s0 = preCompInfo.S0; + BigInteger s1 = preCompInfo.S1; + // d0 = s[0] + mu*s[1]; mu is either 1 or -1 BigInteger d0; if (mu == 1) { - d0 = s[0].Add(s[1]); + d0 = s0.Add(s1); } else { - d0 = s[0].Subtract(s[1]); + d0 = s0.Subtract(s1); } - BigInteger[] v = GetLucas(mu, m, true); - BigInteger vm = v[1]; - - SimpleBigDecimal lambda0 = ApproximateDivisionByN( - k, s[0], vm, a, m, c); - - SimpleBigDecimal lambda1 = ApproximateDivisionByN( - k, s[1], vm, a, m, c); + int m = curve.FieldSize; + SimpleBigDecimal lambda0 = ApproximateDivisionByN(k, s0, vm, a, m, c); + SimpleBigDecimal lambda1 = ApproximateDivisionByN(k, s1, vm, a, m, c); ZTauElement q = Round(lambda0, lambda1, mu); // r0 = n - d0*q0 - 2*s1*q1 BigInteger r0 = k.Subtract(d0.Multiply(q.u)).Subtract( - BigInteger.ValueOf(2).Multiply(s[1]).Multiply(q.v)); + s1.Multiply(q.v).ShiftLeft(1)); // r1 = s1*q0 - s0*q1 - BigInteger r1 = s[1].Multiply(q.u).Subtract(s[0].Multiply(q.v)); - + BigInteger r1 = s1.Multiply(q.u).Subtract(s0.Multiply(q.v)); + return new ZTauElement(r0, r1); } @@ -651,11 +620,10 @@ namespace Org.BouncyCastle.Math.EC.Abc public static AbstractF2mPoint MultiplyRTnaf(AbstractF2mPoint p, BigInteger k) { AbstractF2mCurve curve = (AbstractF2mCurve)p.Curve; - int m = curve.FieldSize; int a = curve.A.ToBigInteger().IntValue; sbyte mu = GetMu(a); - BigInteger[] s = curve.GetSi(); - ZTauElement rho = PartModReduction(k, m, (sbyte)a, s, mu, (sbyte)10); + + ZTauElement rho = PartModReduction(curve, k, (sbyte)a, mu, (sbyte)10); return MultiplyTnaf(p, rho); } @@ -675,9 +643,7 @@ namespace Org.BouncyCastle.Math.EC.Abc sbyte mu = GetMu(curve.A); sbyte[] u = TauAdicNaf(mu, lambda); - AbstractF2mPoint q = MultiplyFromTnaf(p, u); - - return q; + return MultiplyFromTnaf(p, u); } /** @@ -729,10 +695,9 @@ namespace Org.BouncyCastle.Math.EC.Abc * @return The <code>[τ]</code>-adic window NAF of * <code>λ</code>. */ - public static sbyte[] TauAdicWNaf(sbyte mu, ZTauElement lambda, - sbyte width, BigInteger pow2w, BigInteger tw, ZTauElement[] alpha) + public static sbyte[] TauAdicWNaf(sbyte mu, ZTauElement lambda, int width, int tw, ZTauElement[] alpha) { - if (!((mu == 1) || (mu == -1))) + if (!(mu == 1 || mu == -1)) throw new ArgumentException("mu must be 1 or -1"); BigInteger norm = Norm(mu, lambda); @@ -746,8 +711,10 @@ namespace Org.BouncyCastle.Math.EC.Abc // The array holding the TNAF sbyte[] u = new sbyte[maxLength]; + int pow2Width = 1 << width; + // 2^(width - 1) - BigInteger pow2wMin1 = pow2w.ShiftRight(1); + int pow2wMin1 = pow2Width >> 1; // Split lambda into two BigIntegers to simplify calculations BigInteger r0 = lambda.u; @@ -755,65 +722,39 @@ namespace Org.BouncyCastle.Math.EC.Abc int i = 0; // while lambda <> (0, 0) - while (!((r0.Equals(BigInteger.Zero))&&(r1.Equals(BigInteger.Zero)))) + while (!(r0.Equals(BigInteger.Zero) && r1.Equals(BigInteger.Zero))) { // if r0 is odd if (r0.TestBit(0)) { - // uUnMod = r0 + r1*tw Mod 2^width - BigInteger uUnMod - = r0.Add(r1.Multiply(tw)).Mod(pow2w); - - sbyte uLocal; - // if uUnMod >= 2^(width - 1) - if (uUnMod.CompareTo(pow2wMin1) >= 0) - { - uLocal = (sbyte) uUnMod.Subtract(pow2w).IntValue; - } - else - { - uLocal = (sbyte) uUnMod.IntValue; - } - // uLocal is now in [-2^(width-1), 2^(width-1)-1] - - u[i] = uLocal; - bool s = true; - if (uLocal < 0) - { - s = false; - uLocal = (sbyte)-uLocal; - } - // uLocal is now >= 0 + int uUnMod = (r0.IntValue + (r1.IntValue * tw)) & (pow2Width - 1); - if (s) + if (uUnMod >= pow2wMin1) { - r0 = r0.Subtract(alpha[uLocal].u); - r1 = r1.Subtract(alpha[uLocal].v); + u[i] = (sbyte)(uUnMod - pow2Width); + r0 = r0.Add(alpha[pow2Width - uUnMod].u); + r1 = r1.Add(alpha[pow2Width - uUnMod].v); } else { - r0 = r0.Add(alpha[uLocal].u); - r1 = r1.Add(alpha[uLocal].v); + u[i] = (sbyte)uUnMod; + r0 = r0.Subtract(alpha[uUnMod].u); + r1 = r1.Subtract(alpha[uUnMod].v); } } - else - { - u[i] = 0; - } - BigInteger t = r0; + ++i; + BigInteger t = r0.ShiftRight(1); if (mu == 1) { - r0 = r1.Add(r0.ShiftRight(1)); + r0 = r1.Add(t); } - else + else // mu == -1 { - // mu == -1 - r0 = r1.Subtract(r0.ShiftRight(1)); + r0 = r1.Subtract(t); } - r1 = t.ShiftRight(1).Negate(); - i++; + r1 = t.Negate(); } return u; } @@ -831,7 +772,7 @@ namespace Org.BouncyCastle.Math.EC.Abc AbstractF2mPoint[] pu = new AbstractF2mPoint[(uint)(alphaTnaf.Length + 1) >> 1]; pu[0] = p; - uint precompLen = (uint)alphaTnaf.Length; + int precompLen = alphaTnaf.Length; for (uint i = 3; i < precompLen; i += 2) { pu[i >> 1] = Tnaf.MultiplyFromTnaf(p, alphaTnaf[i]); @@ -841,5 +782,50 @@ namespace Org.BouncyCastle.Math.EC.Abc return pu; } + + private sealed class PartModPreCompCallback + : IPreCompCallback + { + private readonly AbstractF2mCurve m_curve; + private readonly sbyte m_mu; + private readonly bool m_doV; + + internal PartModPreCompCallback(AbstractF2mCurve curve, sbyte mu, bool doV) + { + m_curve = curve; + m_mu = mu; + m_doV = doV; + } + + public PreCompInfo Precompute(PreCompInfo existing) + { + if (existing is PartModPreCompInfo) + return existing; + + var lucas = GetLucas(m_mu, m_curve.FieldSize, m_doV)[1]; + var si = GetSi(m_curve); + + return new PartModPreCompInfo(lucas, si[0], si[1]); + } + } + + private sealed class PartModPreCompInfo + : PreCompInfo + { + private readonly BigInteger m_lucas; + private readonly BigInteger m_s0; + private readonly BigInteger m_s1; + + internal PartModPreCompInfo(BigInteger lucas, BigInteger s0, BigInteger s1) + { + m_lucas = lucas; + m_s0 = s0; + m_s1 = s1; + } + + internal BigInteger Lucas => m_lucas; + internal BigInteger S0 => m_s0; + internal BigInteger S1 => m_s1; + } } } |