Port custom curve for secp256r1 from Java

1 files changed, 283 insertions, 0 deletions

diff --git a/crypto/src/math/ec/custom/sec/SecP256R1Point.cs b/crypto/src/math/ec/custom/sec/SecP256R1Point.cs
new file mode 100644
index 000000000..11e79678f
--- /dev/null
+++ b/crypto/src/math/ec/custom/sec/SecP256R1Point.cs
@@ -0,0 +1,283 @@
+using System;
+
+namespace Org.BouncyCastle.Math.EC.Custom.Sec
+{
+    internal class SecP256R1Point
+        : ECPointBase
+    {
+        /**
+         * 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 SecP256R1Point(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 SecP256R1Point(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 SecP256R1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, bool withCompression)
+            : base(curve, x, y, zs, withCompression)
+        {
+        }
+
+        protected internal override bool CompressionYTilde
+        {
+            get { return this.AffineYCoord.TestBitZero(); }
+        }
+
+        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;
+
+            SecP256R1FieldElement X1 = (SecP256R1FieldElement)this.RawXCoord, Y1 = (SecP256R1FieldElement)this.RawYCoord;
+            SecP256R1FieldElement X2 = (SecP256R1FieldElement)b.RawXCoord, Y2 = (SecP256R1FieldElement)b.RawYCoord;
+
+            SecP256R1FieldElement Z1 = (SecP256R1FieldElement)this.RawZCoords[0];
+            SecP256R1FieldElement Z2 = (SecP256R1FieldElement)b.RawZCoords[0];
+
+            uint[] tt1 = Nat256.CreateExt();
+            uint[] tt2 = Nat256.CreateExt();
+            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;
+                SecP256R1Field.Square(Z1.x, S2);
+
+                U2 = tt2;
+                SecP256R1Field.Multiply(S2, X2.x, U2);
+
+                SecP256R1Field.Multiply(S2, Z1.x, S2);
+                SecP256R1Field.Multiply(S2, Y2.x, S2);
+            }
+
+            bool Z2IsOne = Z2.IsOne;
+            uint[] U1, S1;
+            if (Z2IsOne)
+            {
+                U1 = X1.x;
+                S1 = Y1.x;
+            }
+            else
+            {
+                S1 = t4;
+                SecP256R1Field.Square(Z2.x, S1);
+
+                U1 = tt1;
+                SecP256R1Field.Multiply(S1, X1.x, U1);
+
+                SecP256R1Field.Multiply(S1, Z2.x, S1);
+                SecP256R1Field.Multiply(S1, Y1.x, S1);
+            }
+
+            uint[] H = Nat256.Create();
+            SecP256R1Field.Subtract(U1, U2, H);
+
+            uint[] R = tt2;
+            SecP256R1Field.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;
+            SecP256R1Field.Square(H, HSquared);
+
+            uint[] G = Nat256.Create();
+            SecP256R1Field.Multiply(HSquared, H, G);
+
+            uint[] V = t3;
+            SecP256R1Field.Multiply(HSquared, U1, V);
+
+            Nat256.Mul(S1, G, tt1);
+
+            SecP256R1FieldElement X3 = new SecP256R1FieldElement(t4);
+            SecP256R1Field.Square(R, X3.x);
+            SecP256R1Field.Add(X3.x, G, X3.x);
+            SecP256R1Field.Subtract(X3.x, V, X3.x);
+            SecP256R1Field.Subtract(X3.x, V, X3.x);
+
+            SecP256R1FieldElement Y3 = new SecP256R1FieldElement(G);
+            SecP256R1Field.Subtract(V, X3.x, Y3.x);
+            Nat256.Mul(Y3.x, R, tt2);
+            SecP256R1Field.SubtractExt(tt2, tt1, tt2);
+            SecP256R1Field.Reduce(tt2, Y3.x);
+
+            SecP256R1FieldElement Z3 = new SecP256R1FieldElement(H);
+            if (!Z1IsOne)
+            {
+                SecP256R1Field.Multiply(Z3.x, Z1.x, Z3.x);
+            }
+            if (!Z2IsOne)
+            {
+                SecP256R1Field.Multiply(Z3.x, Z2.x, Z3.x);
+            }
+
+            ECFieldElement[] zs = new ECFieldElement[]{ Z3 };
+
+            return new SecP256R1Point(curve, X3, Y3, zs, IsCompressed);
+        }
+
+        public override ECPoint Twice()
+        {
+            if (this.IsInfinity)
+                return this;
+
+            ECCurve curve = this.Curve;
+
+            SecP256R1FieldElement Y1 = (SecP256R1FieldElement)this.RawYCoord;
+            if (Y1.IsZero)
+                return curve.Infinity;
+
+            SecP256R1FieldElement X1 = (SecP256R1FieldElement)this.RawXCoord, Z1 = (SecP256R1FieldElement)this.RawZCoords[0];
+
+            uint[] t1 = Nat256.Create();
+            uint[] t2 = Nat256.Create();
+
+            uint[] Y1Squared = Nat256.Create();
+            SecP256R1Field.Square(Y1.x, Y1Squared);
+
+            uint[] T = Nat256.Create();
+            SecP256R1Field.Square(Y1Squared, T);
+
+            bool Z1IsOne = Z1.IsOne;
+
+            uint[] Z1Squared = Z1.x;
+            if (!Z1IsOne)
+            {
+                Z1Squared = t2;
+                SecP256R1Field.Square(Z1.x, Z1Squared);
+            }
+
+            SecP256R1Field.Subtract(X1.x, Z1Squared, t1);
+
+            uint[] M = t2;
+            SecP256R1Field.Add(X1.x, Z1Squared, M);
+            SecP256R1Field.Multiply(M, t1, M);
+            SecP256R1Field.Twice(M, t1);
+            SecP256R1Field.Add(M, t1, M);
+
+            uint[] S = Y1Squared;
+            SecP256R1Field.Multiply(Y1Squared, X1.x, S);
+            SecP256R1Field.Twice(S, S);
+            SecP256R1Field.Twice(S, S);
+
+            SecP256R1Field.Twice(T, t1);
+            SecP256R1Field.Twice(t1, t1);
+            SecP256R1Field.Twice(t1, t1);
+
+            SecP256R1FieldElement X3 = new SecP256R1FieldElement(T);
+            SecP256R1Field.Square(M, X3.x);
+            SecP256R1Field.Subtract(X3.x, S, X3.x);
+            SecP256R1Field.Subtract(X3.x, S, X3.x);
+
+            SecP256R1FieldElement Y3 = new SecP256R1FieldElement(S);
+            SecP256R1Field.Subtract(S, X3.x, Y3.x);
+            SecP256R1Field.Multiply(Y3.x, M, Y3.x);
+            SecP256R1Field.Subtract(Y3.x, t1, Y3.x);
+
+            SecP256R1FieldElement Z3 = new SecP256R1FieldElement(M);
+            SecP256R1Field.Twice(Y1.x, Z3.x);
+            if (!Z1IsOne)
+            {
+                SecP256R1Field.Multiply(Z3.x, Z1.x, Z3.x);
+            }
+
+            return new SecP256R1Point(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 Subtract(ECPoint b)
+        {
+            if (b.IsInfinity)
+                return this;
+
+            return Add(b.Negate());
+        }
+
+        public override ECPoint Negate()
+        {
+            if (IsInfinity)
+                return this;
+
+            return new SecP256R1Point(Curve, RawXCoord, RawYCoord.Negate(), RawZCoords, IsCompressed);
+        }
+    }
+}