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org.bouncycastle.math.ec.custom.sec.SecP224K1FieldElement Maven / Gradle / Ivy
package org.bouncycastle.math.ec.custom.sec;
import java.math.BigInteger;
import org.bouncycastle.math.ec.ECFieldElement;
import org.bouncycastle.math.raw.Nat224;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.encoders.Hex;
public class SecP224K1FieldElement extends ECFieldElement.AbstractFp
{
public static final BigInteger Q = new BigInteger(1,
Hex.decodeStrict("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFE56D"));
// Calculated as ECConstants.TWO.modPow(Q.shiftRight(2), Q)
private static final int[] PRECOMP_POW2 = new int[]{ 0x33bfd202, 0xdcfad133, 0x2287624a, 0xc3811ba8,
0xa85558fc, 0x1eaef5d7, 0x8edf154c };
protected int[] x;
public SecP224K1FieldElement(BigInteger x)
{
if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0)
{
throw new IllegalArgumentException("x value invalid for SecP224K1FieldElement");
}
this.x = SecP224K1Field.fromBigInteger(x);
}
public SecP224K1FieldElement()
{
this.x = Nat224.create();
}
protected SecP224K1FieldElement(int[] x)
{
this.x = x;
}
public boolean isZero()
{
return Nat224.isZero(x);
}
public boolean isOne()
{
return Nat224.isOne(x);
}
public boolean testBitZero()
{
return Nat224.getBit(x, 0) == 1;
}
public BigInteger toBigInteger()
{
return Nat224.toBigInteger(x);
}
public String getFieldName()
{
return "SecP224K1Field";
}
public int getFieldSize()
{
return Q.bitLength();
}
public ECFieldElement add(ECFieldElement b)
{
int[] z = Nat224.create();
SecP224K1Field.add(x, ((SecP224K1FieldElement)b).x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement addOne()
{
int[] z = Nat224.create();
SecP224K1Field.addOne(x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement subtract(ECFieldElement b)
{
int[] z = Nat224.create();
SecP224K1Field.subtract(x, ((SecP224K1FieldElement)b).x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement multiply(ECFieldElement b)
{
int[] z = Nat224.create();
SecP224K1Field.multiply(x, ((SecP224K1FieldElement)b).x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement divide(ECFieldElement b)
{
// return multiply(b.invert());
int[] z = Nat224.create();
SecP224K1Field.inv(((SecP224K1FieldElement)b).x, z);
SecP224K1Field.multiply(z, x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement negate()
{
int[] z = Nat224.create();
SecP224K1Field.negate(x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement square()
{
int[] z = Nat224.create();
SecP224K1Field.square(x, z);
return new SecP224K1FieldElement(z);
}
public ECFieldElement invert()
{
// return new SecP224K1FieldElement(toBigInteger().modInverse(Q));
int[] z = Nat224.create();
SecP224K1Field.inv(x, z);
return new SecP224K1FieldElement(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()
{
/*
* Q == 8m + 5, so we use Pocklington's method for this case.
*
* First, raise this element to the exponent 2^221 - 2^29 - 2^9 - 2^8 - 2^6 - 2^4 - 2^1 (i.e. m + 1)
*
* Breaking up the exponent's binary representation into "repunits", we get:
* { 191 1s } { 1 0s } { 19 1s } { 2 0s } { 1 1s } { 1 0s } { 1 1s } { 1 0s } { 3 1s } { 1 0s }
*
* Therefore we need an addition chain containing 1, 3, 19, 191 (the lengths of the repunits)
* We use: [1], 2, [3], 4, 8, 11, [19], 23, 42, 84, 107, [191]
*/
int[] x1 = this.x;
if (Nat224.isZero(x1) || Nat224.isOne(x1))
{
return this;
}
int[] x2 = Nat224.create();
SecP224K1Field.square(x1, x2);
SecP224K1Field.multiply(x2, x1, x2);
int[] x3 = x2;
SecP224K1Field.square(x2, x3);
SecP224K1Field.multiply(x3, x1, x3);
int[] x4 = Nat224.create();
SecP224K1Field.square(x3, x4);
SecP224K1Field.multiply(x4, x1, x4);
int[] x8 = Nat224.create();
SecP224K1Field.squareN(x4, 4, x8);
SecP224K1Field.multiply(x8, x4, x8);
int[] x11 = Nat224.create();
SecP224K1Field.squareN(x8, 3, x11);
SecP224K1Field.multiply(x11, x3, x11);
int[] x19 = x11;
SecP224K1Field.squareN(x11, 8, x19);
SecP224K1Field.multiply(x19, x8, x19);
int[] x23 = x8;
SecP224K1Field.squareN(x19, 4, x23);
SecP224K1Field.multiply(x23, x4, x23);
int[] x42 = x4;
SecP224K1Field.squareN(x23, 19, x42);
SecP224K1Field.multiply(x42, x19, x42);
int[] x84 = Nat224.create();
SecP224K1Field.squareN(x42, 42, x84);
SecP224K1Field.multiply(x84, x42, x84);
int[] x107 = x42;
SecP224K1Field.squareN(x84, 23, x107);
SecP224K1Field.multiply(x107, x23, x107);
int[] x191 = x23;
SecP224K1Field.squareN(x107, 84, x191);
SecP224K1Field.multiply(x191, x84, x191);
int[] t1 = x191;
SecP224K1Field.squareN(t1, 20, t1);
SecP224K1Field.multiply(t1, x19, t1);
SecP224K1Field.squareN(t1, 3, t1);
SecP224K1Field.multiply(t1, x1, t1);
SecP224K1Field.squareN(t1, 2, t1);
SecP224K1Field.multiply(t1, x1, t1);
SecP224K1Field.squareN(t1, 4, t1);
SecP224K1Field.multiply(t1, x3, t1);
SecP224K1Field.square(t1, t1);
int[] t2 = x84;
SecP224K1Field.square(t1, t2);
if (Nat224.eq(x1, t2))
{
return new SecP224K1FieldElement(t1);
}
/*
* If the first guess is incorrect, we multiply by a precomputed power of 2 to get the second guess,
* which is ((4x)^(m + 1))/2 mod Q
*/
SecP224K1Field.multiply(t1, PRECOMP_POW2, t1);
SecP224K1Field.square(t1, t2);
if (Nat224.eq(x1, t2))
{
return new SecP224K1FieldElement(t1);
}
return null;
}
public boolean equals(Object other)
{
if (other == this)
{
return true;
}
if (!(other instanceof SecP224K1FieldElement))
{
return false;
}
SecP224K1FieldElement o = (SecP224K1FieldElement)other;
return Nat224.eq(x, o.x);
}
public int hashCode()
{
return Q.hashCode() ^ Arrays.hashCode(x, 0, 7);
}
}
