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;
/**
* Implements the Segmented Integer Counter (SIC) mode on top of a simple
* block cipher. This mode is also known as CTR mode.
*/
public class SICBlockCipher implements BlockCipher
{
private BlockCipher cipher = null;
private int blockSize;
private byte[] IV;
private byte[] counter;
private byte[] counterOut;
private boolean encrypting;
/**
* Basic constructor.
*
* @param c the block cipher to be used.
*/
public SICBlockCipher(BlockCipher c) {
this.cipher = c;
this.blockSize = cipher.getBlockSize();
this.IV = new byte[blockSize];
this.counter = new byte[blockSize];
this.counterOut = 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;
}
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException {
this.encrypting = forEncryption;
if (params instanceof ParametersWithIV) {
ParametersWithIV ivParam = (ParametersWithIV)params;
byte[] iv = ivParam.getIV();
System.arraycopy(iv, 0, IV, 0, IV.length);
reset();
cipher.init(true, ivParam.getParameters());
}
}
public String getAlgorithmName()
{
return cipher.getAlgorithmName() + "/SIC";
}
public int getBlockSize()
{
return cipher.getBlockSize();
}
public int processBlock(byte[] in, int inOff, byte[] out, int outOff)
throws DataLengthException, IllegalStateException {
cipher.processBlock(counter, 0, counterOut, 0);
//
// XOR the counterOut with the plaintext producing the cipher text
//
for (int i = 0; i < counterOut.length; i++) {
out[outOff + i] = (byte)(counterOut[i] ^ in[inOff + i]);
}
int carry = 1;
for (int i = counter.length - 1; i >= 0; i--)
{
int x = (counter[i] & 0xff) + carry;
if (x > 0xff)
{
carry = 1;
}
else
{
carry = 0;
}
counter[i] = (byte)x;
}
return counter.length;
}
public void reset() {
System.arraycopy(IV, 0, counter, 0, counter.length);
cipher.reset();
}
}