1 files changed, 298 insertions, 0 deletions
diff --git a/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1Point.java b/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1Point.java
new file mode 100644
index 0000000..f57b200
--- /dev/null
+++ b/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1Point.java
@@ -0,0 +1,298 @@
+package org.bouncycastle.math.ec.custom.sec;
+
+import org.bouncycastle.math.ec.ECCurve;
+import org.bouncycastle.math.ec.ECFieldElement;
+import org.bouncycastle.math.ec.ECPoint;
+import org.bouncycastle.math.raw.Nat;
+import org.bouncycastle.math.raw.Nat256;
+
+public class SecP256K1Point extends ECPoint.AbstractFp
+{
+    /**
+     * 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(boolean)}
+     */
+    public SecP256K1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, boolean withCompression)
+    {
+        super(curve, x, y);
+
+        if ((x == null) != (y == null))
+        {
+            throw new IllegalArgumentException("Exactly one of the field elements is null");
+        }
+
+        this.withCompression = withCompression;
+    }
+
+    SecP256K1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs,
+        boolean withCompression)
+    {
+        super(curve, x, y, zs);
+
+        this.withCompression = withCompression;
+    }
+
+    protected ECPoint detach()
+    {
+        return new SecP256K1Point(null, getAffineXCoord(), getAffineYCoord());
+    }
+
+    // B.3 pg 62
+    public ECPoint add(ECPoint b)
+    {
+        if (this.isInfinity())
+        {
+            return b;
+        }
+        if (b.isInfinity())
+        {
+            return this;
+        }
+        if (this == b)
+        {
+            return twice();
+        }
+
+        ECCurve curve = this.getCurve();
+
+        SecP256K1FieldElement X1 = (SecP256K1FieldElement)this.x, Y1 = (SecP256K1FieldElement)this.y;
+        SecP256K1FieldElement X2 = (SecP256K1FieldElement)b.getXCoord(), Y2 = (SecP256K1FieldElement)b.getYCoord();
+
+        SecP256K1FieldElement Z1 = (SecP256K1FieldElement)this.zs[0];
+        SecP256K1FieldElement Z2 = (SecP256K1FieldElement)b.getZCoord(0);
+
+        int c;
+        int[] tt1 = Nat256.createExt();
+        int[] t2 = Nat256.create();
+        int[] t3 = Nat256.create();
+        int[] t4 = Nat256.create();
+
+        boolean Z1IsOne = Z1.isOne();
+        int[] 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);
+        }
+
+        boolean Z2IsOne = Z2.isOne();
+        int[] 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);
+        }
+
+        int[] H = Nat256.create();
+        SecP256K1Field.subtract(U1, U2, H);
+
+        int[] 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.getInfinity();
+        }
+
+        int[] HSquared = t3;
+        SecP256K1Field.square(H, HSquared);
+
+        int[] G = Nat256.create();
+        SecP256K1Field.multiply(HSquared, H, G);
+
+        int[] 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, this.withCompression);
+    }
+
+    // B.3 pg 62
+    public ECPoint twice()
+    {
+        if (this.isInfinity())
+        {
+            return this;
+        }
+
+        ECCurve curve = this.getCurve();
+
+        SecP256K1FieldElement Y1 = (SecP256K1FieldElement)this.y;
+        if (Y1.isZero())
+        {
+            return curve.getInfinity();
+        }
+
+        SecP256K1FieldElement X1 = (SecP256K1FieldElement)this.x, Z1 = (SecP256K1FieldElement)this.zs[0];
+
+        int c;
+        
+        int[] Y1Squared = Nat256.create();
+        SecP256K1Field.square(Y1.x, Y1Squared);
+
+        int[] T = Nat256.create();
+        SecP256K1Field.square(Y1Squared, T);
+
+        int[] M = Nat256.create();
+        SecP256K1Field.square(X1.x, M);
+        c = Nat256.addBothTo(M, M, M);
+        SecP256K1Field.reduce32(c, M);
+
+        int[] S = Y1Squared;
+        SecP256K1Field.multiply(Y1Squared, X1.x, S);
+        c = Nat.shiftUpBits(8, S, 2, 0);
+        SecP256K1Field.reduce32(c, S);
+
+        int[] 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 }, this.withCompression);
+    }
+
+    public ECPoint twicePlus(ECPoint b)
+    {
+        if (this == b)
+        {
+            return threeTimes();
+        }
+        if (this.isInfinity())
+        {
+            return b;
+        }
+        if (b.isInfinity())
+        {
+            return twice();
+        }
+
+        ECFieldElement Y1 = this.y;
+        if (Y1.isZero())
+        {
+            return b;
+        }
+
+        return twice().add(b);
+    }
+
+    public ECPoint threeTimes()
+    {
+        if (this.isInfinity() || this.y.isZero())
+        {
+            return this;
+        }
+
+        // NOTE: Be careful about recursions between twicePlus and threeTimes
+        return twice().add(this);
+    }
+
+    public ECPoint negate()
+    {
+        if (this.isInfinity())
+        {
+            return this;
+        }
+
+        return new SecP256K1Point(curve, this.x, this.y.negate(), this.zs, this.withCompression);
+    }
+}