cryptix.provider.mode

Class FeedbackMode

java.lang.Object

xjava.security.IJCE_Traceable

xjava.security.Cipher

xjava.security.Mode

cryptix.provider.mode.FeedbackMode

All Implemented Interfaces:

FeedbackCipher, Parameterized, SymmetricCipher

Direct Known Subclasses:

CBC, CFB, OFB, PCBC

abstract class FeedbackMode
extends Mode
implements FeedbackCipher, SymmetricCipher

FeedbackMode is used to provide the functionality of an encryption mode, such as CBC, CFB, or OFB, that works as a feedback cipher, where the size of the IV and feedback buffer are equal to the cipher's block size.

It is internal to Cryptix, and not intended to be used directly by applications.

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

$Revision: 1.5 $

Since:

Cryptix 2.2.2

Author:

David Hopwood, Raif S. Naffah

Field Summary

Fields

Modifier and Type	Field and Description
protected int	currentByte Index into the ivBlock.
protected byte[]	ivBlock Value of the current feedback register/queue/buffer.
protected byte[]	ivStart Value of the IV at initialisation phase as supplied by user.
protected int	length Size of the feedback register/queue/buffer.

Fields inherited from class xjava.security.Mode

cipher

Fields inherited from class xjava.security.Cipher

DECRYPT, ENCRYPT, UNINITIALIZED

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	FeedbackMode(boolean implBuffering, boolean implPadding, java.lang.String provider) Constructor for a Mode.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	engineSetCipher(Cipher cipher) SPI: Sets the underlying cipher.
byte[]	getInitializationVector() Gets a copy of the starting initialization vector.
int	getInitializationVectorLength() Returns the size of the initialization vector expected by setInitializationVector.
void	setInitializationVector(byte[] iv) Sets the initialization vector.

Methods inherited from class xjava.security.Mode

engineGetParameter, 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, engineInBufferSize, engineInitDecrypt, engineInitEncrypt, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, engineUpdate, getAlgorithm, getCiphertextBlockSize, getInputBlockSize, getInstance, getMode, getOutputBlockSize, getPadding, getPaddingScheme, getParameter, getPlaintextBlockSize, getProvider, getState, inBufferSize, inBufferSizeFinal, initDecrypt, initEncrypt, isPaddingBlockCipher, outBufferSize, outBufferSizeFinal, setParameter, update, update, update, update

Methods inherited from class java.lang.Object

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

Field Detail

ivBlock

protected byte[] ivBlock

Value of the current feedback register/queue/buffer.

ivStart

protected byte[] ivStart

Value of the IV at initialisation phase as supplied by user.

currentByte

protected int currentByte

Index into the ivBlock.

length

protected int length

Size of the feedback register/queue/buffer.

Constructor Detail

FeedbackMode

protected FeedbackMode(boolean implBuffering,
            boolean implPadding,
            java.lang.String provider)

Constructor for a Mode. This constructor is only for use by subclasses, which should pass the correct arguments to convey their behaviour to the superclass. Applications typically do not use Mode classes directly; they should call one of the Cipher.getInstance factory methods instead.

Parameters:

implBuffering - if true, this argument indicates that data will be passed from update/crypt to engineUpdate/engineCrypt without modification.

implPadding - if true, this argument indicates that the implementation can perform padding, and that the engineCrypt method will be called when padding is required.

provider - the name of the provider of the underlying cryptographic engine.

Throws:

java.lang.NullPointerException - if provider == null

Method Detail

engineSetCipher

protected void engineSetCipher(Cipher cipher)

SPI: Sets the underlying cipher.

For example, to create an IDEA cipher in CBC mode, the cipher for "IDEA" would be passed to the mode for "CBC" using this method. It is called once, immediately after the mode object is constructed.

Subclasses that override this method (to do initialization that depends on the cipher being set) should call super.engineSetCipher(cipher) first.

Overrides:

engineSetCipher in class Mode

Parameters:

cipher - the underlying cipher object

Throws:

java.lang.NullPointerException - if cipher == null

setInitializationVector

public void setInitializationVector(byte[] iv)
                             throws java.security.InvalidParameterException

Sets the initialization vector.

Note: in JavaSoft's version of JCE, this method may only be called when the cipher is in the UNINITIALIZED state. In IJCE that is relaxed to also allow it to be called after initEncrypt/initDecrypt, but before the first call to update or crypt, provided that the IV is not set twice.

Specified by:

setInitializationVector in interface FeedbackCipher

Parameters:

iv - the initialization vector.

Throws:

java.security.InvalidParameterException - if the initialization vector is of the wrong length or has already been set.

getInitializationVector

public byte[] getInitializationVector()

Gets a copy of the starting initialization vector. It will return null if the initialization vector has not been set.

Specified by:

getInitializationVector in interface FeedbackCipher

Returns:

a copy of the initialization vector for this cipher object.

getInitializationVectorLength

public int getInitializationVectorLength()

Returns the size of the initialization vector expected by setInitializationVector. For this class, that is the block size of the underlying cipher.

Specified by:

getInitializationVectorLength in interface FeedbackCipher

Returns:

the required size of the argument to setInitializationVector.