org.bouncycastle.crypto.modes

Class OFBBlockCipher

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
StringgetAlgorithmName()
return the algorithm name and mode.
intgetBlockSize()
return the block size we are operating at (in bytes).
BlockCiphergetUnderlyingCipher()
return the underlying block cipher that we are wrapping.
voidinit(boolean encrypting, CipherParameters params)
Initialise the cipher and, possibly, the initialisation vector (IV).
intprocessBlock(byte[] in, int inOff, byte[] out, int outOff)
Process one block of input from the array in and write it to the out array.
voidreset()
reset the feedback vector back to the IV and reset the underlying cipher.

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

getAlgorithmName

public String getAlgorithmName()
return the algorithm name and mode.

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).

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)
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.

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: IllegalArgumentException if the params argument is inappropriate.

processBlock

public 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.

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.