diff options
Diffstat (limited to 'crypto/src/math/ec/ECAlgorithms.cs')
| -rw-r--r-- | crypto/src/math/ec/ECAlgorithms.cs | 170 |
1 files changed, 91 insertions, 79 deletions
diff --git a/crypto/src/math/ec/ECAlgorithms.cs b/crypto/src/math/ec/ECAlgorithms.cs index be4fd1b14..06288132b 100644 --- a/crypto/src/math/ec/ECAlgorithms.cs +++ b/crypto/src/math/ec/ECAlgorithms.cs @@ -1,93 +1,105 @@ using System; -using Org.BouncyCastle.Math; +using Org.BouncyCastle.Math.Field; namespace Org.BouncyCastle.Math.EC { - public class ECAlgorithms - { - public static ECPoint SumOfTwoMultiplies(ECPoint P, BigInteger a, - ECPoint Q, BigInteger b) - { - ECCurve c = P.Curve; - if (!c.Equals(Q.Curve)) - throw new ArgumentException("P and Q must be on same curve"); + public class ECAlgorithms + { + public static bool IsF2mCurve(ECCurve c) + { + IFiniteField field = c.Field; + return field.Dimension > 1 && field.Characteristic.Equals(BigInteger.Two) + && field is IPolynomialExtensionField; + } - // Point multiplication for Koblitz curves (using WTNAF) beats Shamir's trick - if (c is F2mCurve) - { - F2mCurve f2mCurve = (F2mCurve) c; - if (f2mCurve.IsKoblitz) - { - return P.Multiply(a).Add(Q.Multiply(b)); - } - } + public static bool IsFpCurve(ECCurve c) + { + return c.Field.Dimension == 1; + } - return ImplShamirsTrick(P, a, Q, b); - } + public static ECPoint SumOfTwoMultiplies(ECPoint P, BigInteger a, + ECPoint Q, BigInteger b) + { + ECCurve c = P.Curve; + if (!c.Equals(Q.Curve)) + throw new ArgumentException("P and Q must be on same curve"); - /* - * "Shamir's Trick", originally due to E. G. Straus - * (Addition chains of vectors. American Mathematical Monthly, - * 71(7):806-808, Aug./Sept. 1964) - * - * Input: The points P, Q, scalar k = (km?, ... , k1, k0) - * and scalar l = (lm?, ... , l1, l0). - * Output: R = k * P + l * Q. - * 1: Z <- P + Q - * 2: R <- O - * 3: for i from m-1 down to 0 do - * 4: R <- R + R {point doubling} - * 5: if (ki = 1) and (li = 0) then R <- R + P end if - * 6: if (ki = 0) and (li = 1) then R <- R + Q end if - * 7: if (ki = 1) and (li = 1) then R <- R + Z end if - * 8: end for - * 9: return R - */ - public static ECPoint ShamirsTrick( - ECPoint P, - BigInteger k, - ECPoint Q, - BigInteger l) - { - if (!P.Curve.Equals(Q.Curve)) - throw new ArgumentException("P and Q must be on same curve"); + // Point multiplication for Koblitz curves (using WTNAF) beats Shamir's trick + if (c is F2mCurve) + { + F2mCurve f2mCurve = (F2mCurve) c; + if (f2mCurve.IsKoblitz) + { + return P.Multiply(a).Add(Q.Multiply(b)); + } + } - return ImplShamirsTrick(P, k, Q, l); - } + return ImplShamirsTrick(P, a, Q, b); + } - private static ECPoint ImplShamirsTrick(ECPoint P, BigInteger k, - ECPoint Q, BigInteger l) - { - int m = System.Math.Max(k.BitLength, l.BitLength); - ECPoint Z = P.Add(Q); - ECPoint R = P.Curve.Infinity; + /* + * "Shamir's Trick", originally due to E. G. Straus + * (Addition chains of vectors. American Mathematical Monthly, + * 71(7):806-808, Aug./Sept. 1964) + * + * Input: The points P, Q, scalar k = (km?, ... , k1, k0) + * and scalar l = (lm?, ... , l1, l0). + * Output: R = k * P + l * Q. + * 1: Z <- P + Q + * 2: R <- O + * 3: for i from m-1 down to 0 do + * 4: R <- R + R {point doubling} + * 5: if (ki = 1) and (li = 0) then R <- R + P end if + * 6: if (ki = 0) and (li = 1) then R <- R + Q end if + * 7: if (ki = 1) and (li = 1) then R <- R + Z end if + * 8: end for + * 9: return R + */ + public static ECPoint ShamirsTrick( + ECPoint P, + BigInteger k, + ECPoint Q, + BigInteger l) + { + if (!P.Curve.Equals(Q.Curve)) + throw new ArgumentException("P and Q must be on same curve"); - for (int i = m - 1; i >= 0; --i) - { - R = R.Twice(); + return ImplShamirsTrick(P, k, Q, l); + } - if (k.TestBit(i)) - { - if (l.TestBit(i)) - { - R = R.Add(Z); - } - else - { - R = R.Add(P); - } - } - else - { - if (l.TestBit(i)) - { - R = R.Add(Q); - } - } - } + private static ECPoint ImplShamirsTrick(ECPoint P, BigInteger k, + ECPoint Q, BigInteger l) + { + int m = System.Math.Max(k.BitLength, l.BitLength); + ECPoint Z = P.Add(Q); + ECPoint R = P.Curve.Infinity; - return R; - } - } + for (int i = m - 1; i >= 0; --i) + { + R = R.Twice(); + + if (k.TestBit(i)) + { + if (l.TestBit(i)) + { + R = R.Add(Z); + } + else + { + R = R.Add(P); + } + } + else + { + if (l.TestBit(i)) + { + R = R.Add(Q); + } + } + } + + return R; + } + } } |