diff options
Diffstat (limited to 'crypto/src/math/ec/custom/sec/SecP256R1FieldElement.cs')
| -rw-r--r-- | crypto/src/math/ec/custom/sec/SecP256R1FieldElement.cs | 38 |
1 files changed, 36 insertions, 2 deletions
diff --git a/crypto/src/math/ec/custom/sec/SecP256R1FieldElement.cs b/crypto/src/math/ec/custom/sec/SecP256R1FieldElement.cs index a4a7004c0..650f12aaf 100644 --- a/crypto/src/math/ec/custom/sec/SecP256R1FieldElement.cs +++ b/crypto/src/math/ec/custom/sec/SecP256R1FieldElement.cs @@ -126,8 +126,42 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec */ public override ECFieldElement Sqrt() { - ECFieldElement root = new FpFieldElement(Q, ToBigInteger()).Sqrt(); - return root == null ? null : new SecP256R1FieldElement(root.ToBigInteger()); + // Raise this element to the exponent 2^254 - 2^222 + 2^190 + 2^94 + + uint[] x1 = this.x; + if (Nat256.IsZero(x1) || Nat256.IsOne(x1)) + { + return this; + } + + uint[] t1 = Nat256.Create(); + uint[] t2 = Nat256.Create(); + + SecP256R1Field.Square(x1, t1); + SecP256R1Field.Multiply(t1, x1, t1); + + SecP256R1Field.SquareN(t1, 2, t2); + SecP256R1Field.Multiply(t2, t1, t2); + + SecP256R1Field.SquareN(t2, 4, t1); + SecP256R1Field.Multiply(t1, t2, t1); + + SecP256R1Field.SquareN(t1, 8, t2); + SecP256R1Field.Multiply(t2, t1, t2); + + SecP256R1Field.SquareN(t2, 16, t1); + SecP256R1Field.Multiply(t1, t2, t1); + + SecP256R1Field.SquareN(t1, 32, t1); + SecP256R1Field.Multiply(t1, x1, t1); + + SecP256R1Field.SquareN(t1, 96, t1); + SecP256R1Field.Multiply(t1, x1, t1); + + SecP256R1Field.SquareN(t1, 94, t1); + SecP256R1Field.Multiply(t1, t1, t2); + + return Arrays.AreEqual(x1, t2) ? new SecP256R1FieldElement(t1) : null; } public override bool Equals(object obj) |