diff options
Diffstat (limited to 'crypto/src/math/ec/custom/sec/SecP256K1Point.cs')
| -rw-r--r-- | crypto/src/math/ec/custom/sec/SecP256K1Point.cs | 265 |
1 files changed, 265 insertions, 0 deletions
diff --git a/crypto/src/math/ec/custom/sec/SecP256K1Point.cs b/crypto/src/math/ec/custom/sec/SecP256K1Point.cs new file mode 100644 index 000000000..3165682fa --- /dev/null +++ b/crypto/src/math/ec/custom/sec/SecP256K1Point.cs @@ -0,0 +1,265 @@ +using System; + +namespace Org.BouncyCastle.Math.EC.Custom.Sec +{ + internal class SecP256K1Point + : AbstractFpPoint + { + /** + * Create a point which encodes with point compression. + * + * @param curve + * the curve to use + * @param x + * affine x co-ordinate + * @param y + * affine y co-ordinate + * + * @deprecated Use ECCurve.createPoint to construct points + */ + public SecP256K1Point(ECCurve curve, ECFieldElement x, ECFieldElement y) + : this(curve, x, y, false) + { + } + + /** + * Create a point that encodes with or without point compresion. + * + * @param curve + * the curve to use + * @param x + * affine x co-ordinate + * @param y + * affine y co-ordinate + * @param withCompression + * if true encode with point compression + * + * @deprecated per-point compression property will be removed, refer + * {@link #getEncoded(bool)} + */ + public SecP256K1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, bool withCompression) + : base(curve, x, y, withCompression) + { + if ((x == null) != (y == null)) + throw new ArgumentException("Exactly one of the field elements is null"); + } + + internal SecP256K1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, + bool withCompression) + : base(curve, x, y, zs, withCompression) + { + } + + protected override ECPoint Detach() + { + return new SecP256K1Point(null, AffineXCoord, AffineYCoord); + } + + public override ECPoint Add(ECPoint b) + { + if (this.IsInfinity) + return b; + if (b.IsInfinity) + return this; + if (this == b) + return Twice(); + + ECCurve curve = this.Curve; + + SecP256K1FieldElement X1 = (SecP256K1FieldElement)this.RawXCoord, Y1 = (SecP256K1FieldElement)this.RawYCoord; + SecP256K1FieldElement X2 = (SecP256K1FieldElement)b.RawXCoord, Y2 = (SecP256K1FieldElement)b.RawYCoord; + + SecP256K1FieldElement Z1 = (SecP256K1FieldElement)this.RawZCoords[0]; + SecP256K1FieldElement Z2 = (SecP256K1FieldElement)b.RawZCoords[0]; + + uint c; + uint[] tt1 = Nat256.CreateExt(); + uint[] t2 = Nat256.Create(); + uint[] t3 = Nat256.Create(); + uint[] t4 = Nat256.Create(); + + bool Z1IsOne = Z1.IsOne; + uint[] U2, S2; + if (Z1IsOne) + { + U2 = X2.x; + S2 = Y2.x; + } + else + { + S2 = t3; + SecP256K1Field.Square(Z1.x, S2); + + U2 = t2; + SecP256K1Field.Multiply(S2, X2.x, U2); + + SecP256K1Field.Multiply(S2, Z1.x, S2); + SecP256K1Field.Multiply(S2, Y2.x, S2); + } + + bool Z2IsOne = Z2.IsOne; + uint[] U1, S1; + if (Z2IsOne) + { + U1 = X1.x; + S1 = Y1.x; + } + else + { + S1 = t4; + SecP256K1Field.Square(Z2.x, S1); + + U1 = tt1; + SecP256K1Field.Multiply(S1, X1.x, U1); + + SecP256K1Field.Multiply(S1, Z2.x, S1); + SecP256K1Field.Multiply(S1, Y1.x, S1); + } + + uint[] H = Nat256.Create(); + SecP256K1Field.Subtract(U1, U2, H); + + uint[] R = t2; + SecP256K1Field.Subtract(S1, S2, R); + + // Check if b == this or b == -this + if (Nat256.IsZero(H)) + { + if (Nat256.IsZero(R)) + { + // this == b, i.e. this must be doubled + return this.Twice(); + } + + // this == -b, i.e. the result is the point at infinity + return curve.Infinity; + } + + uint[] HSquared = t3; + SecP256K1Field.Square(H, HSquared); + + uint[] G = Nat256.Create(); + SecP256K1Field.Multiply(HSquared, H, G); + + uint[] V = t3; + SecP256K1Field.Multiply(HSquared, U1, V); + + SecP256K1Field.Negate(G, G); + Nat256.Mul(S1, G, tt1); + + c = Nat256.AddBothTo(V, V, G); + SecP256K1Field.Reduce32(c, G); + + SecP256K1FieldElement X3 = new SecP256K1FieldElement(t4); + SecP256K1Field.Square(R, X3.x); + SecP256K1Field.Subtract(X3.x, G, X3.x); + + SecP256K1FieldElement Y3 = new SecP256K1FieldElement(G); + SecP256K1Field.Subtract(V, X3.x, Y3.x); + SecP256K1Field.MultiplyAddToExt(Y3.x, R, tt1); + SecP256K1Field.Reduce(tt1, Y3.x); + + SecP256K1FieldElement Z3 = new SecP256K1FieldElement(H); + if (!Z1IsOne) + { + SecP256K1Field.Multiply(Z3.x, Z1.x, Z3.x); + } + if (!Z2IsOne) + { + SecP256K1Field.Multiply(Z3.x, Z2.x, Z3.x); + } + + ECFieldElement[] zs = new ECFieldElement[] { Z3 }; + + return new SecP256K1Point(curve, X3, Y3, zs, IsCompressed); + } + + public override ECPoint Twice() + { + if (this.IsInfinity) + return this; + + ECCurve curve = this.Curve; + + SecP256K1FieldElement Y1 = (SecP256K1FieldElement)this.RawYCoord; + if (Y1.IsZero) + return curve.Infinity; + + SecP256K1FieldElement X1 = (SecP256K1FieldElement)this.RawXCoord, Z1 = (SecP256K1FieldElement)this.RawZCoords[0]; + + uint c; + + uint[] Y1Squared = Nat256.Create(); + SecP256K1Field.Square(Y1.x, Y1Squared); + + uint[] T = Nat256.Create(); + SecP256K1Field.Square(Y1Squared, T); + + uint[] M = Nat256.Create(); + SecP256K1Field.Square(X1.x, M); + c = Nat256.AddBothTo(M, M, M); + SecP256K1Field.Reduce32(c, M); + + uint[] S = Y1Squared; + SecP256K1Field.Multiply(Y1Squared, X1.x, S); + c = Nat.ShiftUpBits(8, S, 2, 0); + SecP256K1Field.Reduce32(c, S); + + uint[] t1 = Nat256.Create(); + c = Nat.ShiftUpBits(8, T, 3, 0, t1); + SecP256K1Field.Reduce32(c, t1); + + SecP256K1FieldElement X3 = new SecP256K1FieldElement(T); + SecP256K1Field.Square(M, X3.x); + SecP256K1Field.Subtract(X3.x, S, X3.x); + SecP256K1Field.Subtract(X3.x, S, X3.x); + + SecP256K1FieldElement Y3 = new SecP256K1FieldElement(S); + SecP256K1Field.Subtract(S, X3.x, Y3.x); + SecP256K1Field.Multiply(Y3.x, M, Y3.x); + SecP256K1Field.Subtract(Y3.x, t1, Y3.x); + + SecP256K1FieldElement Z3 = new SecP256K1FieldElement(M); + SecP256K1Field.Twice(Y1.x, Z3.x); + if (!Z1.IsOne) + { + SecP256K1Field.Multiply(Z3.x, Z1.x, Z3.x); + } + + return new SecP256K1Point(curve, X3, Y3, new ECFieldElement[] { Z3 }, IsCompressed); + } + + public override ECPoint TwicePlus(ECPoint b) + { + if (this == b) + return ThreeTimes(); + if (this.IsInfinity) + return b; + if (b.IsInfinity) + return Twice(); + + ECFieldElement Y1 = this.RawYCoord; + if (Y1.IsZero) + return b; + + return Twice().Add(b); + } + + public override ECPoint ThreeTimes() + { + if (this.IsInfinity || this.RawYCoord.IsZero) + return this; + + // NOTE: Be careful about recursions between TwicePlus and ThreeTimes + return Twice().Add(this); + } + + public override ECPoint Negate() + { + if (IsInfinity) + return this; + + return new SecP256K1Point(Curve, RawXCoord, RawYCoord.Negate(), RawZCoords, IsCompressed); + } + } +} |