org.bouncycastle.crypto.modes
Class CBCBlockCipher

java.lang.Object
  org.bouncycastle.crypto.modes.CBCBlockCipher

All Implemented Interfaces:

BlockCipher

public class CBCBlockCipher
extends java.lang.Object
implements BlockCipher

implements Cipher-Block-Chaining (CBC) mode on top of a simple cipher.

Field Summary

private int	blockSize
private byte[]	cbcNextV
private byte[]	cbcV
private BlockCipher	cipher
private boolean	encrypting
private byte[]	IV

Constructor Summary

CBCBlockCipher(BlockCipher cipher)
Basic constructor.

Method Summary

private int	decryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate chaining step for CBC mode decryption.
private int	encryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate chaining step for CBC mode encryption.
java.lang.String	getAlgorithmName() return the algorithm name and mode.
int	getBlockSize() return the block size of the underlying cipher.
BlockCipher	getUnderlyingCipher() return the underlying block cipher that we are wrapping.
void	init(boolean encrypting, CipherParameters params) Initialise the cipher and, possibly, the initialisation vector (IV).
int	processBlock(byte[] in, int inOff, byte[] out, int outOff) Process one block of input from the array in and write it to the out array.
void	reset() reset the chaining vector back to the IV and reset the underlying cipher.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

IV

private byte[] IV

cbcV

private byte[] cbcV

cbcNextV

private byte[] cbcNextV

blockSize

private int blockSize

cipher

private BlockCipher cipher

encrypting

private boolean encrypting

Constructor Detail

CBCBlockCipher

public CBCBlockCipher(BlockCipher cipher)

Basic constructor.

Parameters:

cipher - the block cipher to be used as the basis of chaining.

Method Detail

getUnderlyingCipher

public BlockCipher getUnderlyingCipher()

return the underlying block cipher that we are wrapping.

Returns:

the underlying block cipher that we are wrapping.

init

public void init(boolean encrypting,
                 CipherParameters params)
          throws java.lang.IllegalArgumentException

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.

Specified by:

init in interface BlockCipher

Parameters:

encrypting - if true the cipher is initialised for encryption, if false for decryption.

params - the key and other data required by the cipher.

Throws:

java.lang.IllegalArgumentException - if the params argument is inappropriate.

getAlgorithmName

public java.lang.String getAlgorithmName()

return the algorithm name and mode.

Specified by:

getAlgorithmName in interface BlockCipher

Returns:

the name of the underlying algorithm followed by "/CBC".

getBlockSize

public int getBlockSize()

return the block size of the underlying cipher.

Specified by:

getBlockSize in interface BlockCipher

Returns:

the block size of the underlying cipher.

processBlock

public int processBlock(byte[] in,
                        int inOff,
                        byte[] out,
                        int outOff)
                 throws DataLengthException,
                        java.lang.IllegalStateException

Process one block of input from the array in and write it to the out array.

Specified by:

processBlock in interface BlockCipher

Parameters:

in - the array containing the input data.

inOff - offset into the in array the data starts at.

out - the array the output data will be copied into.

outOff - the offset into the out array the output will start at.

Returns:

the number of bytes processed and produced.

Throws:

DataLengthException - if there isn't enough data in in, or space in out.

java.lang.IllegalStateException - if the cipher isn't initialised.

reset

public void reset()

reset the chaining vector back to the IV and reset the underlying cipher.

Specified by:

reset in interface BlockCipher

encryptBlock

private int encryptBlock(byte[] in,
                         int inOff,
                         byte[] out,
                         int outOff)
                  throws DataLengthException,
                         java.lang.IllegalStateException

Do the appropriate chaining step for CBC mode encryption.

Parameters:

in - the array containing the data to be encrypted.

inOff - offset into the in array the data starts at.

out - the array the encrypted data will be copied into.

outOff - the offset into the out array the output will start at.

Returns:

the number of bytes processed and produced.

Throws:

DataLengthException - if there isn't enough data in in, or space in out.

java.lang.IllegalStateException - if the cipher isn't initialised.

decryptBlock

private int decryptBlock(byte[] in,
                         int inOff,
                         byte[] out,
                         int outOff)
                  throws DataLengthException,
                         java.lang.IllegalStateException

Do the appropriate chaining step for CBC mode decryption.

Parameters:

in - the array containing the data to be decrypted.

inOff - offset into the in array the data starts at.

out - the array the decrypted data will be copied into.

outOff - the offset into the out array the output will start at.

Returns:

the number of bytes processed and produced.

Throws:

DataLengthException - if there isn't enough data in in, or space in out.

java.lang.IllegalStateException - if the cipher isn't initialised.