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package org.spongycastle.crypto.engines;
import org.spongycastle.crypto.BlockCipher;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.DataLengthException;
import org.spongycastle.crypto.OutputLengthException;
import org.spongycastle.crypto.params.KeyParameter;
/**
* An XTEA engine.
*/
public class XTEAEngine
implements BlockCipher
{
private static final int rounds = 32,
block_size = 8,
// key_size = 16,
delta = 0x9E3779B9;
/*
* the expanded key array of 4 subkeys
*/
private int[] _S = new int[4],
_sum0 = new int[32],
_sum1 = new int[32];
private boolean _initialised,
_forEncryption;
/**
* Create an instance of the TEA encryption algorithm
* and set some defaults
*/
public XTEAEngine()
{
_initialised = false;
}
public String getAlgorithmName()
{
return "XTEA";
}
public int getBlockSize()
{
return block_size;
}
/**
* initialise
*
* @param forEncryption whether or not we are for encryption.
* @param params the parameters required to set up the cipher.
* @exception IllegalArgumentException if the params argument is
* inappropriate.
*/
public void init(
boolean forEncryption,
CipherParameters params)
{
if (!(params instanceof KeyParameter))
{
throw new IllegalArgumentException("invalid parameter passed to TEA init - " + params.getClass().getName());
}
_forEncryption = forEncryption;
_initialised = true;
KeyParameter p = (KeyParameter)params;
setKey(p.getKey());
}
public int processBlock(
byte[] in,
int inOff,
byte[] out,
int outOff)
{
if (!_initialised)
{
throw new IllegalStateException(getAlgorithmName()+" not initialised");
}
if ((inOff + block_size) > in.length)
{
throw new DataLengthException("input buffer too short");
}
if ((outOff + block_size) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
return (_forEncryption) ? encryptBlock(in, inOff, out, outOff)
: decryptBlock(in, inOff, out, outOff);
}
public void reset()
{
}
/**
* Re-key the cipher.
* <p>
* @param key the key to be used
*/
private void setKey(
byte[] key)
{
if (key.length != 16)
{
throw new IllegalArgumentException("Key size must be 128 bits.");
}
int i, j;
for (i = j = 0; i < 4; i++,j+=4)
{
_S[i] = bytesToInt(key, j);
}
for (i = j = 0; i < rounds; i++)
{
_sum0[i] = (j + _S[j & 3]);
j += delta;
_sum1[i] = (j + _S[j >>> 11 & 3]);
}
}
private int encryptBlock(
byte[] in,
int inOff,
byte[] out,
int outOff)
{
// Pack bytes into integers
int v0 = bytesToInt(in, inOff);
int v1 = bytesToInt(in, inOff + 4);
for (int i = 0; i < rounds; i++)
{
v0 += ((v1 << 4 ^ v1 >>> 5) + v1) ^ _sum0[i];
v1 += ((v0 << 4 ^ v0 >>> 5) + v0) ^ _sum1[i];
}
unpackInt(v0, out, outOff);
unpackInt(v1, out, outOff + 4);
return block_size;
}
private int decryptBlock(
byte[] in,
int inOff,
byte[] out,
int outOff)
{
// Pack bytes into integers
int v0 = bytesToInt(in, inOff);
int v1 = bytesToInt(in, inOff + 4);
for (int i = rounds-1; i >= 0; i--)
{
v1 -= ((v0 << 4 ^ v0 >>> 5) + v0) ^ _sum1[i];
v0 -= ((v1 << 4 ^ v1 >>> 5) + v1) ^ _sum0[i];
}
unpackInt(v0, out, outOff);
unpackInt(v1, out, outOff + 4);
return block_size;
}
private int bytesToInt(byte[] in, int inOff)
{
return ((in[inOff++]) << 24) |
((in[inOff++] & 255) << 16) |
((in[inOff++] & 255) << 8) |
((in[inOff] & 255));
}
private void unpackInt(int v, byte[] out, int outOff)
{
out[outOff++] = (byte)(v >>> 24);
out[outOff++] = (byte)(v >>> 16);
out[outOff++] = (byte)(v >>> 8);
out[outOff ] = (byte)v;
}
}
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