diff options
| -rw-r--r-- | crypto/src/math/ec/custom/sec/SecP384R1FieldElement.cs | 58 |
1 files changed, 56 insertions, 2 deletions
diff --git a/crypto/src/math/ec/custom/sec/SecP384R1FieldElement.cs b/crypto/src/math/ec/custom/sec/SecP384R1FieldElement.cs index bca260de9..6e4fd2030 100644 --- a/crypto/src/math/ec/custom/sec/SecP384R1FieldElement.cs +++ b/crypto/src/math/ec/custom/sec/SecP384R1FieldElement.cs @@ -124,8 +124,62 @@ namespace Org.BouncyCastle.Math.EC.Custom.Sec */ public override ECFieldElement Sqrt() { - ECFieldElement root = new FpFieldElement(Q, ToBigInteger()).Sqrt(); - return root == null ? null : new SecP384R1FieldElement(root.ToBigInteger()); + // Raise this element to the exponent 2^382 - 2^126 - 2^94 + 2^30 + + uint[] x1 = this.x; + if (Nat.IsZero(12, x1) || Nat.IsOne(12, x1)) + return this; + + uint[] t1 = Nat.Create(12); + uint[] t2 = Nat.Create(12); + uint[] t3 = Nat.Create(12); + uint[] t4 = Nat.Create(12); + + SecP384R1Field.Square(x1, t1); + SecP384R1Field.Multiply(t1, x1, t1); + + SecP384R1Field.SquareN(t1, 2, t2); + SecP384R1Field.Multiply(t2, t1, t2); + + SecP384R1Field.Square(t2, t2); + SecP384R1Field.Multiply(t2, x1, t2); + + SecP384R1Field.SquareN(t2, 5, t3); + SecP384R1Field.Multiply(t3, t2, t3); + + SecP384R1Field.SquareN(t3, 5, t4); + SecP384R1Field.Multiply(t4, t2, t4); + + SecP384R1Field.SquareN(t4, 15, t2); + SecP384R1Field.Multiply(t2, t4, t2); + + SecP384R1Field.SquareN(t2, 2, t3); + SecP384R1Field.Multiply(t1, t3, t1); + + SecP384R1Field.SquareN(t3, 28, t3); + SecP384R1Field.Multiply(t2, t3, t2); + + SecP384R1Field.SquareN(t2, 60, t3); + SecP384R1Field.Multiply(t3, t2, t3); + + uint[] r = t2; + + SecP384R1Field.SquareN(t3, 120, r); + SecP384R1Field.Multiply(r, t3, r); + + SecP384R1Field.SquareN(r, 15, r); + SecP384R1Field.Multiply(r, t4, r); + + SecP384R1Field.SquareN(r, 33, r); + SecP384R1Field.Multiply(r, t1, r); + + SecP384R1Field.SquareN(r, 64, r); + SecP384R1Field.Multiply(r, x1, r); + + SecP384R1Field.SquareN(r, 30, t1); + SecP384R1Field.Square(t1, t2); + + return Nat.Eq(12, x1, t2) ? new SecP384R1FieldElement(t1) : null; } public override bool Equals(object obj) |