org.spongycastle.crypto.modes

Class CFBBlockCipher

java.lang.Object

org.spongycastle.crypto.StreamBlockCipher

org.spongycastle.crypto.modes.CFBBlockCipher

All Implemented Interfaces:

BlockCipher, StreamCipher

public class CFBBlockCipher
extends StreamBlockCipher

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).
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 org.spongycastle.crypto.StreamBlockCipher

getUnderlyingCipher, processBytes, returnByte

Methods inherited from class java.lang.Object

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

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

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.

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.

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.

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.

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.