org.bouncycastle.crypto.modes

Class CFBBlockCipher

java.lang.Object

org.bouncycastle.crypto.DefaultMultiBlockCipher

org.bouncycastle.crypto.StreamBlockCipher

org.bouncycastle.crypto.modes.CFBBlockCipher

All Implemented Interfaces:

BlockCipher, CFBModeCipher, MultiBlockCipher, StreamCipher

public class CFBBlockCipher
extends StreamBlockCipher
implements CFBModeCipher

implements a Cipher-FeedBack (CFB) mode on top of a simple cipher.

Constructor Summary

Constructors

Constructor and Description
CFBBlockCipher(BlockCipher cipher, int bitBlockSize) Basic constructor.

Method Summary

Modifier and Type	Method and Description
protected byte	calculateByte(byte in)
int	decryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate processing for CFB mode decryption.
int	encryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate processing for CFB mode encryption.
java.lang.String	getAlgorithmName() return the algorithm name and mode.
int	getBlockSize() return the block size we are operating at.
byte[]	getCurrentIV() Return the current state of the initialisation vector.
void	init(boolean encrypting, CipherParameters params) Initialise the cipher and, possibly, the initialisation vector (IV).
static CFBModeCipher	newInstance(BlockCipher cipher, int bitSize) Return a new CFB mode cipher based on the passed in base cipher
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.
java.lang.String	toString()

Methods inherited from class org.bouncycastle.crypto.StreamBlockCipher

getUnderlyingCipher, processBytes, returnByte

Methods inherited from class org.bouncycastle.crypto.DefaultMultiBlockCipher

getMultiBlockSize, processBlocks

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.bouncycastle.crypto.MultiBlockCipher

getMultiBlockSize, processBlocks

Methods inherited from interface org.bouncycastle.crypto.StreamCipher

processBytes, returnByte

Constructor Detail

CFBBlockCipher

public CFBBlockCipher(BlockCipher cipher,
                      int bitBlockSize)

Basic constructor.

Parameters:

cipher - the block cipher to be used as the basis of the feedback mode.

bitBlockSize - the block size in bits (note: a multiple of 8)

Method Detail

newInstance

public static CFBModeCipher newInstance(BlockCipher cipher,
                                        int bitSize)

Return a new CFB mode cipher based on the passed in base cipher

Parameters:

cipher - the base cipher for the CFB mode.

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

Specified by:

init in interface BlockCipher

Specified by:

init in interface StreamCipher

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

Specified by:

getAlgorithmName in interface StreamCipher

Returns:

the name of the underlying algorithm followed by "/CFB" and the block size in bits.

calculateByte

protected byte calculateByte(byte in)
                      throws DataLengthException,
                             java.lang.IllegalStateException

Specified by:

calculateByte in class StreamBlockCipher

Throws:

DataLengthException

java.lang.IllegalStateException

getBlockSize

public int getBlockSize()

return the block size we are operating at.

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,
                        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.

encryptBlock

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

Do the appropriate processing for CFB 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

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

Do the appropriate processing for CFB 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 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.

getCurrentIV

public byte[] getCurrentIV()

Return the current state of the initialisation vector.

Returns:

current IV

reset

public void reset()

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

Specified by:

reset in interface BlockCipher

Specified by:

reset in interface StreamCipher

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object