org.bouncycastle.crypto.modes

Class OFBBlockCipher

Implemented Interfaces:
BlockCipher

public class OFBBlockCipher
extends java.lang.Object
implements BlockCipher

implements a Output-FeedBack (OFB) mode on top of a simple cipher.

Constructor Summary

OFBBlockCipher(BlockCipher cipher, int blockSize)
Basic constructor.

Method Summary

String
getAlgorithmName()
return the algorithm name and mode.
int
getBlockSize()
return the block size we are operating at (in bytes).
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 feedback vector back to the IV and reset the underlying cipher.

Constructor Details

OFBBlockCipher

public OFBBlockCipher(BlockCipher cipher,
                      int blockSize)
Basic constructor.

Parameters:
cipher - the block cipher to be used as the basis of the feedback mode.
blockSize - the block size in bits (note: a multiple of 8)

Method Details

getAlgorithmName

public String getAlgorithmName()
return the algorithm name and mode.
Specified by:
getAlgorithmName in interface BlockCipher

Returns:
the name of the underlying algorithm followed by "/OFB" and the block size in bits


getBlockSize

public int getBlockSize()
return the block size we are operating at (in bytes).
Specified by:
getBlockSize in interface BlockCipher

Returns:
the block size we are operating at (in bytes).


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 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. An IV which is too short is handled in FIPS compliant fashion.
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.


processBlock

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


reset

public void reset()
reset the feedback vector back to the IV and reset the underlying cipher.
Specified by:
reset in interface BlockCipher