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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar
contains APIs for JDK 1.5 and up. The APIs can be used in conjunction with a JCE/JCA provider such as the one
provided with the Bouncy Castle Cryptography APIs.
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;
import org.bouncycastle.util.Arrays;
/**
* implements Cipher-Block-Chaining (CBC) mode on top of a simple cipher.
*/
public class CBCBlockCipher
implements BlockCipher
{
private byte[] IV;
private byte[] cbcV;
private byte[] cbcNextV;
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 CBCBlockCipher(
BlockCipher cipher)
{
this.cipher = cipher;
this.blockSize = cipher.getBlockSize();
this.IV = new byte[blockSize];
this.cbcV = new byte[blockSize];
this.cbcNextV = 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)
{
throw new IllegalArgumentException("initialisation vector must be the same length as block size");
}
System.arraycopy(iv, 0, IV, 0, iv.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 "/CBC".
*/
public String getAlgorithmName()
{
return cipher.getAlgorithmName() + "/CBC";
}
/**
* 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(IV, 0, cbcV, 0, IV.length);
Arrays.fill(cbcNextV, (byte)0);
cipher.reset();
}
/**
* Do the appropriate chaining step for CBC 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");
}
/*
* XOR the cbcV and the input,
* then encrypt the cbcV
*/
for (int i = 0; i < blockSize; i++)
{
cbcV[i] ^= in[inOff + i];
}
int length = cipher.processBlock(cbcV, 0, out, outOff);
/*
* copy ciphertext to cbcV
*/
System.arraycopy(out, outOff, cbcV, 0, cbcV.length);
return length;
}
/**
* Do the appropriate chaining step for CBC 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");
}
System.arraycopy(in, inOff, cbcNextV, 0, blockSize);
int length = cipher.processBlock(in, inOff, out, outOff);
/*
* XOR the cbcV and the output
*/
for (int i = 0; i < blockSize; i++)
{
out[outOff + i] ^= cbcV[i];
}
/*
* swap the back up buffer into next position
*/
byte[] tmp;
tmp = cbcV;
cbcV = cbcNextV;
cbcNextV = tmp;
return length;
}
}