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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 with debug enabled.
package org.bouncycastle.math.ec.custom.sec;
import java.math.BigInteger;
import org.bouncycastle.math.raw.Nat;
import org.bouncycastle.math.raw.Nat512;
public class SecP521R1Field
{
// 2^521 - 1
static final int[] P = new int[]{ 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x1FF };
private static final int P16 = 0x1FF;
public static void add(int[] x, int[] y, int[] z)
{
int c = Nat.add(16, x, y, z) + x[16] + y[16];
if (c > P16 || (c == P16 && Nat.eq(16, z, P)))
{
c += Nat.inc(16, z);
c &= P16;
}
z[16] = c;
}
public static void addOne(int[] x, int[] z)
{
int c = Nat.inc(16, x, z) + x[16];
if (c > P16 || (c == P16 && Nat.eq(16, z, P)))
{
c += Nat.inc(16, z);
c &= P16;
}
z[16] = c;
}
public static int[] fromBigInteger(BigInteger x)
{
int[] z = Nat.fromBigInteger(521, x);
if (Nat.eq(17, z, P))
{
Nat.zero(17, z);
}
return z;
}
public static void half(int[] x, int[] z)
{
int x16 = x[16];
int c = Nat.shiftDownBit(16, x, x16, z);
z[16] = (x16 >>> 1) | (c >>> 23);
}
public static void multiply(int[] x, int[] y, int[] z)
{
int[] tt = Nat.create(33);
implMultiply(x, y, tt);
reduce(tt, z);
}
public static void negate(int[] x, int[] z)
{
if (Nat.isZero(17, x))
{
Nat.zero(17, z);
}
else
{
Nat.sub(17, P, x, z);
}
}
public static void reduce(int[] xx, int[] z)
{
// assert xx[32] >>> 18 == 0;
int xx32 = xx[32];
int c = Nat.shiftDownBits(16, xx, 16, 9, xx32, z, 0) >>> 23;
c += xx32 >>> 9;
c += Nat.addTo(16, xx, z);
if (c > P16 || (c == P16 && Nat.eq(16, z, P)))
{
c += Nat.inc(16, z);
c &= P16;
}
z[16] = c;
}
public static void reduce23(int[] z)
{
int z16 = z[16];
int c = Nat.addWordTo(16, z16 >>> 9, z) + (z16 & P16);
if (c > P16 || (c == P16 && Nat.eq(16, z, P)))
{
c += Nat.inc(16, z);
c &= P16;
}
z[16] = c;
}
public static void square(int[] x, int[] z)
{
int[] tt = Nat.create(33);
implSquare(x, tt);
reduce(tt, z);
}
public static void squareN(int[] x, int n, int[] z)
{
// assert n > 0;
int[] tt = Nat.create(33);
implSquare(x, tt);
reduce(tt, z);
while (--n > 0)
{
implSquare(z, tt);
reduce(tt, z);
}
}
public static void subtract(int[] x, int[] y, int[] z)
{
int c = Nat.sub(16, x, y, z) + x[16] - y[16];
if (c < 0)
{
c += Nat.dec(16, z);
c &= P16;
}
z[16] = c;
}
public static void twice(int[] x, int[] z)
{
int x16 = x[16];
int c = Nat.shiftUpBit(16, x, x16 << 23, z) | (x16 << 1);
z[16] = c & P16;
}
protected static void implMultiply(int[] x, int[] y, int[] zz)
{
Nat512.mul(x, y, zz);
int x16 = x[16], y16 = y[16];
zz[32] = Nat.mul31BothAdd(16, x16, y, y16, x, zz, 16) + (x16 * y16);
}
protected static void implSquare(int[] x, int[] zz)
{
Nat512.square(x, zz);
int x16 = x[16];
zz[32] = Nat.mulWordAddTo(16, x16 << 1, x, 0, zz, 16) + (x16 * x16);
}
}
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