de.flexiprovider.common.mode
Class OFB

java.lang.Object
  |
  +--de.flexiprovider.api.Mode
        |
        +--de.flexiprovider.common.mode.OFB

public class OFB

extends Mode

Output feedback mode for symmetric block ciphers as per ISO/IEC 10116 (full feedback)

We do not support the FIPS PUB 81 version of OFB, since the expected cycle length dramatically decreases if the feedback is smaller than the block size of the cipher.

TODO WARNING! OFB currently supports just 1-byte feedback

For further information, see "Handbook of Applied Cryptography", Note 7.24.

Author:

Ralf-P. Weinmann

Fields inherited from class de.flexiprovider.api.Mode

blockSize, iv

Constructor Summary

OFB()

Method Summary

protected void	initDecrypt(SecretKey key, ModeParameterSpec modeParams, AlgorithmParameterSpec cipherParams) Initialize the Mode object for decryption.
protected void	initEncrypt(SecretKey key, ModeParameterSpec modeParams, AlgorithmParameterSpec cipherParams) Initialize the Mode object for encryption.
protected void	nextChunkDecrypt(byte[] input, int inOff, byte[] output, int outOff) Decrypt the next data block.
protected void	nextChunkEncrypt(byte[] input, int inOff, byte[] output, int outOff) Encrypt the next data block.
protected void	reset() Reset feedback block to encrypted initialization vector.

Methods inherited from class de.flexiprovider.api.Mode

getCipherBlockSize, initCipherDecrypt, initCipherEncrypt, setBlockCipher, singleBlockDecrypt, singleBlockEncrypt

Methods inherited from class java.lang.Object

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

Constructor Detail

OFB

public OFB()

Method Detail

initEncrypt

protected final void initEncrypt(SecretKey key,
                                 ModeParameterSpec modeParams,
                                 AlgorithmParameterSpec cipherParams)
                          throws InvalidKeyException,
                                 InvalidAlgorithmParameterException

Initialize the Mode object for encryption.

Overrides:

initEncrypt in class Mode

Parameters:

key - the key used for encryption

modeParams - additional mode parameters

cipherParams - additional algorithm parameters

Throws:

InvalidKeyException - if the key is inappropriate for initializing the underlying block cipher.

InvalidAlgorithmParameterException - if the parameters are inappropriate for initializing the underlying block cipher.

initDecrypt

protected final void initDecrypt(SecretKey key,
                                 ModeParameterSpec modeParams,
                                 AlgorithmParameterSpec cipherParams)
                          throws InvalidKeyException,
                                 InvalidAlgorithmParameterException

Initialize the Mode object for decryption.

Overrides:

initDecrypt in class Mode

Parameters:

key - the key used for decryption

modeParams - additional mode parameters

cipherParams - additional algorithm parameters

Throws:

InvalidKeyException - if the key is inappropriate for initializing the underlying block cipher.

InvalidAlgorithmParameterException - if the parameters are inappropriate for initializing the underlying block cipher.

nextChunkEncrypt

protected final void nextChunkEncrypt(byte[] input,
                                      int inOff,
                                      byte[] output,
                                      int outOff)

Encrypt the next data block.

Overrides:

nextChunkEncrypt in class Mode

Parameters:

input - input data buffer

inOff - input data offset

output - output data buffer

outOff - output data offset

nextChunkDecrypt

protected final void nextChunkDecrypt(byte[] input,
                                      int inOff,
                                      byte[] output,
                                      int outOff)

Decrypt the next data block.

Overrides:

nextChunkDecrypt in class Mode

Parameters:

input - input data buffer

inOff - input data offset

output - output data buffer

outOff - output data offset

reset

protected final void reset()

Reset feedback block to encrypted initialization vector.

Overrides:

reset in class Mode