cryptix.provider.mode

Class CFB_PGP

Implemented Interfaces:
FeedbackCipher, Parameterized, SymmetricCipher

public class CFB_PGP
extends CFB

Use of this feedback mode is deprecated, use it for compatibility only!

This class implements PGP's (i.e. Zimmerman's) non-standard CFB mode. (For the standard method, see the Applied Cryptography reference below). It replaces cryptix.pgp.CFB in version 2.2, and cryptix.pgp.PGP_CFB in version Cryptix 2.2.0a.

The differences between this and standard CFB are that:

Note that it is unusual for the output of a cipher to depend on the exact boundaries between data passed to each encryption/decryption call. Normally, the lengths of data passed to each call do not matter as long as they make up the correct input when concatenated together - but this class is an exception.

As a result, using this mode with CipherInputStream and CipherOutputStream may produce unexpected output, and is not recommended.

References

  1. Bruce Schneier, "Section 9.6 Cipher Feedback Mode," Applied Cryptography, 2nd edition, John Wiley & Sons, 1996

Copyright © 1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.9 $

Authors:
Systemics Ltd
Raif Naffah
David Hopwood
Since:
Cryptix 2.2.2

Field Summary

Fields inherited from class cryptix.provider.mode.FeedbackMode

currentByte, ivBlock, ivStart, length

Fields inherited from class xjava.security.Mode

cipher

Fields inherited from class xjava.security.Cipher

DECRYPT, ENCRYPT, UNINITIALIZED

Fields inherited from class xjava.security.IJCE_Traceable

tracing

Constructor Summary

CFB_PGP()
Constructs a CFB-PGP cipher, assuming that the IV will be provided as the first getInitializationVectorLength() bytes of the stream (it will be visible as cleartext at the start of the output stream).
CFB_PGP(Cipher cipher)
Constructs a CFB-PGP cipher, assuming that the IV will be provided as the first getInitializationVectorLength() bytes of the stream.

Method Summary

protected int
engineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset)
SPI: This is the main engine method for updating data.

Methods inherited from class cryptix.provider.mode.CFB

engineBlockSize, engineInitDecrypt, engineInitEncrypt, engineSetCipher, engineUpdate, next_block

Methods inherited from class cryptix.provider.mode.FeedbackMode

engineSetCipher, getInitializationVector, getInitializationVectorLength, setInitializationVector

Methods inherited from class xjava.security.Mode

engineGetParameter, engineSetCipher, engineSetParameter, getAlgorithms, getAlgorithms, getInstance, getInstance, toString

Methods inherited from class xjava.security.Cipher

blockSize, clone, crypt, crypt, crypt, doFinal, doFinal, doFinal, doFinal, engineBlockSize, engineCiphertextBlockSize, engineCrypt, engineGetParameter, engineInBufferSize, engineInitDecrypt, engineInitEncrypt, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, engineSetParameter, engineUpdate, getAlgorithm, getAlgorithms, getAlgorithms, getCiphertextBlockSize, getInputBlockSize, getInstance, getInstance, getInstance, getMode, getOutputBlockSize, getPadding, getPaddingScheme, getParameter, getPlaintextBlockSize, getProvider, getState, inBufferSize, inBufferSizeFinal, initDecrypt, initEncrypt, isPaddingBlockCipher, outBufferSize, outBufferSizeFinal, setParameter, toString, update, update, update, update

Methods inherited from class xjava.security.IJCE_Traceable

disableTracing, enableTracing, traceMethod, traceResult, traceResult, traceVoidMethod

Constructor Details

CFB_PGP

public CFB_PGP()
Constructs a CFB-PGP cipher, assuming that the IV will be provided as the first getInitializationVectorLength() bytes of the stream (it will be visible as cleartext at the start of the output stream).

The IV must be unique during the lifetime of the key. If it is not unique, at least the first block of the plaintext can be recovered.


CFB_PGP

public CFB_PGP(Cipher cipher)
Constructs a CFB-PGP cipher, assuming that the IV will be provided as the first getInitializationVectorLength() bytes of the stream. See the previous constructor for more details.

Method Details

engineUpdate

protected int engineUpdate(byte[] in,
                           int inOffset,
                           int inLen,
                           byte[] out,
                           int outOffset)
SPI: This is the main engine method for updating data. It may be called with any size of input.

in and out may be the same array, and the input and output regions may overlap.

Overrides:
engineUpdate in interface CFB
Parameters:
in - the input data.
inOffset - the offset into in specifying where the data starts.
inLen - the length of the subarray.
out - the output array.
outOffset - the offset indicating where to start writing into the out array.
Returns:
the number of bytes written.