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package org.bouncycastle.math.ec.custom.sec;
import java.math.BigInteger;
public class SecP256K1Field
{
private static final long M = 0xFFFFFFFFL;
// 2^256 - 2^32 - 2^9 - 2^8 - 2^7 - 2^6 - 2^4 - 1
private static final int[] P = new int[]{ 0xFFFFFC2F, 0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
0xFFFFFFFF, 0xFFFFFFFF };
private static final int P7 = 0xFFFFFFFF;
private static final long PInv = 0x00000001000003D1L;
public static void add(int[] x, int[] y, int[] z)
{
int c = Nat256.add(x, y, z);
if (c != 0 || (z[7] == P7 && Nat256.gte(z, P)))
{
Nat256.addDWord(PInv, z, 0);
}
}
public static void addOne(int[] x, int[] z)
{
System.arraycopy(x, 0, z, 0, 8);
int c = Nat256.inc(z, 0);
if (c != 0 || (z[7] == P7 && Nat256.gte(z, P)))
{
Nat256.addDWord(PInv, z, 0);
}
}
public static int[] fromBigInteger(BigInteger x)
{
int[] z = Nat256.fromBigInteger(x);
if (z[7] == P7 && Nat256.gte(z, P))
{
Nat256.addDWord(PInv, z, 0);
}
return z;
}
public static void multiply(int[] x, int[] y, int[] z)
{
int[] tt = Nat256.createExt();
Nat256.mul(x, y, tt);
reduce(tt, z);
}
public static void negate(int[] x, int[] z)
{
if (Nat256.isZero(x))
{
Nat256.zero(z);
}
else
{
Nat256.sub(P, x, z);
}
}
private static void reduce(int[] tt, int[] z)
{
long extra = -(tt[8] & M);
extra += Nat256.mulWordAddExt((int)PInv, tt, 8, tt, 0) & M;
extra += (Nat256.addExt(tt, 8, tt, 1) & M) << 32;
extra += (tt[8] & M);
long c = Nat256.mulWordDwordAdd((int)PInv, extra, tt, 0) & M;
c += Nat256.addDWord(extra, tt, 1);
// assert c == 0L || c == 1L;
if (c != 0 || (tt[7] == P7 && Nat256.gte(tt, P)))
{
Nat256.addDWord(PInv, tt, 0);
}
System.arraycopy(tt, 0, z, 0, 8);
}
public static void square(int[] x, int[] z)
{
int[] tt = Nat256.createExt();
Nat256.square(x, tt);
reduce(tt, z);
}
public static void subtract(int[] x, int[] y, int[] z)
{
int c = Nat256.sub(x, y, z);
if (c != 0)
{
Nat256.subDWord(PInv, z);
}
}
}
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