| 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); |
| } |
| } |