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package org.bouncycastle.crypto.modes.gcm;
import org.bouncycastle.crypto.util.Pack;
import org.bouncycastle.util.Arrays;
abstract class GCMUtil
{
static byte[] oneAsBytes()
{
byte[] tmp = new byte[16];
tmp[0] = (byte)0x80;
return tmp;
}
static int[] oneAsInts()
{
int[] tmp = new int[4];
tmp[0] = 0x80000000;
return tmp;
}
static int[] asInts(byte[] bs)
{
int[] us = new int[4];
us[0] = Pack.bigEndianToInt(bs, 0);
us[1] = Pack.bigEndianToInt(bs, 4);
us[2] = Pack.bigEndianToInt(bs, 8);
us[3] = Pack.bigEndianToInt(bs, 12);
return us;
}
static void multiply(byte[] block, byte[] val)
{
byte[] tmp = Arrays.clone(block);
byte[] c = new byte[16];
for (int i = 0; i < 16; ++i)
{
byte bits = val[i];
for (int j = 7; j >= 0; --j)
{
if ((bits & (1 << j)) != 0)
{
xor(c, tmp);
}
boolean lsb = (tmp[15] & 1) != 0;
shiftRight(tmp);
if (lsb)
{
// R = new byte[]{ 0xe1, ... };
// GCMUtil.xor(v, R);
tmp[0] ^= (byte)0xe1;
}
}
}
System.arraycopy(c, 0, block, 0, 16);
}
// P is the value with only bit i=1 set
static void multiplyP(int[] x)
{
boolean lsb = (x[3] & 1) != 0;
shiftRight(x);
if (lsb)
{
// R = new int[]{ 0xe1000000, 0, 0, 0 };
// xor(v, R);
x[0] ^= 0xe1000000;
}
}
static void multiplyP8(int[] x)
{
// for (int i = 8; i != 0; --i)
// {
// multiplyP(x);
// }
int lsw = x[3];
shiftRightN(x, 8);
for (int i = 7; i >= 0; --i)
{
if ((lsw & (1 << i)) != 0)
{
x[0] ^= (0xe1000000 >>> (7 - i));
}
}
}
static void shiftRight(byte[] block)
{
int i = 0;
int bit = 0;
for (;;)
{
int b = block[i] & 0xff;
block[i] = (byte) ((b >>> 1) | bit);
if (++i == 16)
{
break;
}
bit = (b & 1) << 7;
}
}
static void shiftRight(int[] block)
{
int i = 0;
int bit = 0;
for (;;)
{
int b = block[i];
block[i] = (b >>> 1) | bit;
if (++i == 4)
{
break;
}
bit = b << 31;
}
}
static void shiftRightN(int[] block, int n)
{
int i = 0;
int bits = 0;
for (;;)
{
int b = block[i];
block[i] = (b >>> n) | bits;
if (++i == 4)
{
break;
}
bits = b << (32 - n);
}
}
static void xor(byte[] block, byte[] val)
{
for (int i = 15; i >= 0; --i)
{
block[i] ^= val[i];
}
}
static void xor(int[] block, int[] val)
{
for (int i = 3; i >= 0; --i)
{
block[i] ^= val[i];
}
}
}
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