org.gudy.bouncycastle.crypto.modes
Class OFBBlockCipher

java.lang.Object
  extended by org.gudy.bouncycastle.crypto.modes.OFBBlockCipher
All Implemented Interfaces:
BlockCipher

public class OFBBlockCipher
extends 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.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

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 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 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:
forEncryption - if true the cipher is initialised for encryption, if false for decryption.
param - the key and other data required by the cipher.
Throws:
IllegalArgumentException - if the params argument is inappropriate.

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).

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.
IllegalStateException - if the cipher isn't initialised.

reset

public void reset()
reset the feedback vector back to the IV and reset the underlying cipher.

Specified by:
reset in interface BlockCipher