package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.params.ParametersWithIV;
public class IGEBlockCipher implements BlockCipher {
private byte[] x0, y0;
private byte[] xPrev;
private byte[] yPrev;
private int blockSize;
private BlockCipher cipher = null;
private boolean encrypting;
/**
* Basic constructor.
*
* @param cipher the block cipher to be used as the basis of chaining.
*/
public IGEBlockCipher(BlockCipher cipher) {
this.cipher = cipher;
this.blockSize = cipher.getBlockSize();
this.x0 = new byte[blockSize];
this.y0 = new byte[blockSize];
this.xPrev = new byte[blockSize];
this.yPrev = new byte[blockSize];
}
/**
* return the underlying block cipher that we are wrapping.
*
* @return the underlying block cipher that we are wrapping.
*/
public BlockCipher getUnderlyingCipher() {
return cipher;
}
/**
* Initialise the cipher and, possibly, the initialisation vector (IV). If an
* IV isn't passed as part of the parameter, the IV will be all zeros.
*
* @param encrypting if true the cipher is initialised for encryption, if false for decryption.
* @param params the key and other data required by the cipher.
* @exception IllegalArgumentException if the params argument is inappropriate.
*/
public void init(boolean encrypting, CipherParameters params)
throws IllegalArgumentException {
boolean oldEncrypting = this.encrypting;
this.encrypting = encrypting;
if (params instanceof ParametersWithIV) {
ParametersWithIV ivParam = (ParametersWithIV) params;
byte[] iv = ivParam.getIV();
if (iv.length != blockSize * 2) {
throw new IllegalArgumentException(
"initialisation vector must be twice as long as block size");
}
System.arraycopy(iv, 0, x0, 0, x0.length);
System.arraycopy(iv, x0.length, y0, 0, y0.length);
reset();
// if null it's an IV changed only.
if (ivParam.getParameters() != null) {
cipher.init(encrypting, ivParam.getParameters());
} else if (oldEncrypting != encrypting) {
throw new IllegalArgumentException(
"cannot change encrypting state without providing key.");
}
} else {
reset();
// if it's null, key is to be reused.
if (params != null) {
cipher.init(encrypting, params);
} else if (oldEncrypting != encrypting) {
throw new IllegalArgumentException(
"cannot change encrypting state without providing key.");
}
}
}
/**
* return the algorithm name and mode.
*
* @return the name of the underlying algorithm followed by "/IGE".
*/
public String getAlgorithmName() {
return cipher.getAlgorithmName() + "/IGE";
}
/**
* return the block size of the underlying cipher.
*
* @return the block size of the underlying cipher.
*/
public int getBlockSize() {
return cipher.getBlockSize();
}
/**
* Process one block of input from the array in and write it to the out array.
*
* @param in the array containing the input data.
* @param inOff offset into the in array the data starts at.
* @param out the array the output data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
public int processBlock(byte[] in, int inOff, byte[] out, int outOff)
throws DataLengthException, IllegalStateException {
return (encrypting) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(
in, inOff, out, outOff);
}
/**
* reset the chaining vector back to the IV and reset the underlying cipher.
*/
public void reset() {
System.arraycopy(x0, 0, xPrev, 0, x0.length);
System.arraycopy(y0, 0, yPrev, 0, y0.length);
cipher.reset();
}
/**
* Do the appropriate chaining step for IGE mode encryption.
*
* @param in the array containing the data to be encrypted.
* @param inOff offset into the in array the data starts at.
* @param out the array the encrypted data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
private int encryptBlock(byte[] in, int inOff, byte[] out, int outOff)
throws DataLengthException, IllegalStateException {
if ((inOff + blockSize) > in.length) {
throw new DataLengthException("input buffer too short");
}
for (int i = 0; i < blockSize; i++) {
xPrev[i] ^= in[inOff + i];
}
int length = cipher.processBlock(xPrev, 0, out, outOff);
for (int i = 0; i < blockSize; i++) {
out[outOff + i] ^= yPrev[i];
}
System.arraycopy(in, inOff, yPrev, 0, yPrev.length);
System.arraycopy(out, outOff, xPrev, 0, xPrev.length);
return length;
}
/**
* Do the appropriate chaining step for IGE mode decryption.
*
* @param in the array containing the data to be decrypted.
* @param inOff offset into the in array the data starts at.
* @param out the array the decrypted data will be copied into.
* @param outOff the offset into the out array the output will start at.
* @exception DataLengthException if there isn't enough data in in, or space in out.
* @exception IllegalStateException if the cipher isn't initialised.
* @return the number of bytes processed and produced.
*/
private int decryptBlock(byte[] in, int inOff, byte[] out, int outOff)
throws DataLengthException, IllegalStateException {
if ((inOff + blockSize) > in.length) {
throw new DataLengthException("input buffer too short");
}
for (int i = 0; i < blockSize; i++) {
yPrev[i] ^= in[inOff + i];
}
int length = cipher.processBlock(yPrev, 0, out, outOff);
for (int i = 0; i < blockSize; i++) {
out[outOff + i] ^= xPrev[i];
}
System.arraycopy(out, outOff, yPrev, 0, yPrev.length);
System.arraycopy(in, inOff, xPrev, 0, xPrev.length);
return length;
}
}