1 files changed, 189 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP256R1FieldElement.java b/core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP256R1FieldElement.java
new file mode 100644
index 00000000..ddbab1a3
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP256R1FieldElement.java
@@ -0,0 +1,189 @@
+package org.spongycastle.math.ec.custom.sec;
+
+import java.math.BigInteger;
+
+import org.spongycastle.math.ec.ECFieldElement;
+import org.spongycastle.math.raw.Mod;
+import org.spongycastle.math.raw.Nat256;
+import org.spongycastle.util.Arrays;
+
+public class SecP256R1FieldElement extends ECFieldElement
+{
+    public static final BigInteger Q = SecP256R1Curve.q;
+
+    protected int[] x;
+
+    public SecP256R1FieldElement(BigInteger x)
+    {
+        if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0)
+        {
+            throw new IllegalArgumentException("x value invalid for SecP256R1FieldElement");
+        }
+
+        this.x = SecP256R1Field.fromBigInteger(x);
+    }
+
+    public SecP256R1FieldElement()
+    {
+        this.x = Nat256.create();
+    }
+
+    protected SecP256R1FieldElement(int[] x)
+    {
+        this.x = x;
+    }
+
+    public boolean isZero()
+    {
+        return Nat256.isZero(x);
+    }
+
+    public boolean isOne()
+    {
+        return Nat256.isOne(x);
+    }
+
+    public boolean testBitZero()
+    {
+        return Nat256.getBit(x, 0) == 1;
+    }
+
+    public BigInteger toBigInteger()
+    {
+        return Nat256.toBigInteger(x);
+    }
+
+    public String getFieldName()
+    {
+        return "SecP256R1Field";
+    }
+
+    public int getFieldSize()
+    {
+        return Q.bitLength();
+    }
+
+    public ECFieldElement add(ECFieldElement b)
+    {
+        int[] z = Nat256.create();
+        SecP256R1Field.add(x, ((SecP256R1FieldElement)b).x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement addOne()
+    {
+        int[] z = Nat256.create();
+        SecP256R1Field.addOne(x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement subtract(ECFieldElement b)
+    {
+        int[] z = Nat256.create();
+        SecP256R1Field.subtract(x, ((SecP256R1FieldElement)b).x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement multiply(ECFieldElement b)
+    {
+        int[] z = Nat256.create();
+        SecP256R1Field.multiply(x, ((SecP256R1FieldElement)b).x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement divide(ECFieldElement b)
+    {
+//        return multiply(b.invert());
+        int[] z = Nat256.create();
+        Mod.invert(SecP256R1Field.P, ((SecP256R1FieldElement)b).x, z);
+        SecP256R1Field.multiply(z, x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement negate()
+    {
+        int[] z = Nat256.create();
+        SecP256R1Field.negate(x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement square()
+    {
+        int[] z = Nat256.create();
+        SecP256R1Field.square(x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    public ECFieldElement invert()
+    {
+//        return new SecP256R1FieldElement(toBigInteger().modInverse(Q));
+        int[] z = Nat256.create();
+        Mod.invert(SecP256R1Field.P, x, z);
+        return new SecP256R1FieldElement(z);
+    }
+
+    /**
+     * return a sqrt root - the routine verifies that the calculation returns the right value - if
+     * none exists it returns null.
+     */
+    public ECFieldElement sqrt()
+    {
+        // Raise this element to the exponent 2^254 - 2^222 + 2^190 + 2^94
+
+        int[] x1 = this.x;
+        if (Nat256.isZero(x1) || Nat256.isOne(x1))
+        {
+            return this;
+        }
+
+        int[] t1 = Nat256.create();
+        int[] 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.square(t1, t2);
+
+        return Nat256.eq(x1, t2) ? new SecP256R1FieldElement(t1) : null;
+    }
+
+    public boolean equals(Object other)
+    {
+        if (other == this)
+        {
+            return true;
+        }
+
+        if (!(other instanceof SecP256R1FieldElement))
+        {
+            return false;
+        }
+
+        SecP256R1FieldElement o = (SecP256R1FieldElement)other;
+        return Nat256.eq(x, o.x);
+    }
+
+    public int hashCode()
+    {
+        return Q.hashCode() ^ Arrays.hashCode(x, 0, 8);
+    }
+}