package org.bouncycastle.crypto.engines;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.params.KeyParameter;

An XTEA engine.
/** * 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
/** * 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
Params:
  • forEncryption – whether or not we are for encryption.
  • params – the parameters required to set up the cipher.
Throws:
/** * 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 DataLengthException("output buffer too short"); } return (_forEncryption) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff); } public void reset() { }
Re-key the cipher.

Params:
  • key – the key to be used
/** * Re-key the cipher. * <p> * @param key the key to be used */
private void setKey( byte[] key) { 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; } }