diff options
| -rw-r--r-- | crypto/src/math/ec/ECFieldElement.cs | 20 |
1 files changed, 6 insertions, 14 deletions
diff --git a/crypto/src/math/ec/ECFieldElement.cs b/crypto/src/math/ec/ECFieldElement.cs index 6956baa04..e589fc737 100644 --- a/crypto/src/math/ec/ECFieldElement.cs +++ b/crypto/src/math/ec/ECFieldElement.cs @@ -266,9 +266,7 @@ namespace Org.BouncyCastle.Math.EC if (q.TestBit(2)) // q == 8m + 5 { - BigInteger m = q.ShiftRight(3); - - BigInteger t1 = x.ModPow(m, q); + BigInteger t1 = x.ModPow(q.ShiftRight(3), q); BigInteger t2 = ModMult(t1, x); BigInteger t3 = ModMult(t2, t1); @@ -277,31 +275,25 @@ namespace Org.BouncyCastle.Math.EC return CheckSqrt(new FpFieldElement(q, r, t2)); } - BigInteger e = m.Add(BigInteger.One); - // TODO This is constant and could be precomputed - BigInteger t4 = BigInteger.ValueOf(4).ModPow(e, q); -// BigInteger t4 = BigInteger.Two.ModPow(e.ShiftLeft(1), q); + BigInteger t4 = BigInteger.Two.ModPow(q.ShiftRight(2), q); BigInteger y = ModMult(t2, t4); - return CheckSqrt(new FpFieldElement(q, r, ModHalfAbs(y))); + return CheckSqrt(new FpFieldElement(q, r, y)); } // q == 8m + 1 - BigInteger qMinusOne = q.Subtract(BigInteger.One); - - BigInteger legendreExponent = qMinusOne.ShiftRight(1); + BigInteger legendreExponent = q.ShiftRight(1); if (!(x.ModPow(legendreExponent, q).Equals(BigInteger.One))) return null; - BigInteger u = qMinusOne.ShiftRight(2); - BigInteger k = u.ShiftLeft(1).Add(BigInteger.One); - BigInteger X = this.x; BigInteger fourX = ModDouble(ModDouble(X)); ; + BigInteger k = legendreExponent.Add(BigInteger.One), qMinusOne = q.Subtract(BigInteger.One); + BigInteger U, V; Random rand = new Random(); do |