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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
package org.bouncycastle.math.ec.custom.sec;
import java.math.BigInteger;
import org.bouncycastle.math.ec.ECFieldElement;
import org.bouncycastle.math.raw.Mod;
import org.bouncycastle.math.raw.Nat128;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.encoders.Hex;
public class SecP128R1FieldElement extends ECFieldElement.AbstractFp
{
public static final BigInteger Q = new BigInteger(1,
Hex.decodeStrict("FFFFFFFDFFFFFFFFFFFFFFFFFFFFFFFF"));
protected int[] x;
public SecP128R1FieldElement(BigInteger x)
{
if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0)
{
throw new IllegalArgumentException("x value invalid for SecP128R1FieldElement");
}
this.x = SecP128R1Field.fromBigInteger(x);
}
public SecP128R1FieldElement()
{
this.x = Nat128.create();
}
protected SecP128R1FieldElement(int[] x)
{
this.x = x;
}
public boolean isZero()
{
return Nat128.isZero(x);
}
public boolean isOne()
{
return Nat128.isOne(x);
}
public boolean testBitZero()
{
return Nat128.getBit(x, 0) == 1;
}
public BigInteger toBigInteger()
{
return Nat128.toBigInteger(x);
}
public String getFieldName()
{
return "SecP128R1Field";
}
public int getFieldSize()
{
return Q.bitLength();
}
public ECFieldElement add(ECFieldElement b)
{
int[] z = Nat128.create();
SecP128R1Field.add(x, ((SecP128R1FieldElement)b).x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement addOne()
{
int[] z = Nat128.create();
SecP128R1Field.addOne(x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement subtract(ECFieldElement b)
{
int[] z = Nat128.create();
SecP128R1Field.subtract(x, ((SecP128R1FieldElement)b).x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement multiply(ECFieldElement b)
{
int[] z = Nat128.create();
SecP128R1Field.multiply(x, ((SecP128R1FieldElement)b).x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement divide(ECFieldElement b)
{
// return multiply(b.invert());
int[] z = Nat128.create();
Mod.invert(SecP128R1Field.P, ((SecP128R1FieldElement)b).x, z);
SecP128R1Field.multiply(z, x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement negate()
{
int[] z = Nat128.create();
SecP128R1Field.negate(x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement square()
{
int[] z = Nat128.create();
SecP128R1Field.square(x, z);
return new SecP128R1FieldElement(z);
}
public ECFieldElement invert()
{
// return new SecP128R1FieldElement(toBigInteger().modInverse(Q));
int[] z = Nat128.create();
Mod.invert(SecP128R1Field.P, x, z);
return new SecP128R1FieldElement(z);
}
// D.1.4 91
/**
* 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 2^126 - 2^95
*
* Breaking up the exponent's binary representation into "repunits", we get:
* { 31 1s } { 95 0s }
*
* Therefore we need an addition chain containing 31 (the length of the repunit) We use:
* 1, 2, 4, 8, 10, 20, 30, [31]
*/
int[] x1 = this.x;
if (Nat128.isZero(x1) || Nat128.isOne(x1))
{
return this;
}
int[] x2 = Nat128.create();
SecP128R1Field.square(x1, x2);
SecP128R1Field.multiply(x2, x1, x2);
int[] x4 = Nat128.create();
SecP128R1Field.squareN(x2, 2, x4);
SecP128R1Field.multiply(x4, x2, x4);
int[] x8 = Nat128.create();
SecP128R1Field.squareN(x4, 4, x8);
SecP128R1Field.multiply(x8, x4, x8);
int[] x10 = x4;
SecP128R1Field.squareN(x8, 2, x10);
SecP128R1Field.multiply(x10, x2, x10);
int[] x20 = x2;
SecP128R1Field.squareN(x10, 10, x20);
SecP128R1Field.multiply(x20, x10, x20);
int[] x30 = x8;
SecP128R1Field.squareN(x20, 10, x30);
SecP128R1Field.multiply(x30, x10, x30);
int[] x31 = x10;
SecP128R1Field.square(x30, x31);
SecP128R1Field.multiply(x31, x1, x31);
int[] t1 = x31;
SecP128R1Field.squareN(t1, 95, t1);
int[] t2 = x30;
SecP128R1Field.square(t1, t2);
return Nat128.eq(x1, t2) ? new SecP128R1FieldElement(t1) : null;
}
public boolean equals(Object other)
{
if (other == this)
{
return true;
}
if (!(other instanceof SecP128R1FieldElement))
{
return false;
}
SecP128R1FieldElement o = (SecP128R1FieldElement)other;
return Nat128.eq(x, o.x);
}
public int hashCode()
{
return Q.hashCode() ^ Arrays.hashCode(x, 0, 4);
}
}
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