cryptix.provider.mode

Class FeedbackMode

Implemented Interfaces:
FeedbackCipher, Parameterized, SymmetricCipher
Known Direct Subclasses:
CBC, CFB, OFB, PCBC

(package private) 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 $

Authors:
David Hopwood
Raif S. Naffah

Since:
Cryptix 2.2.2

Field Summary

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

Fields inherited from class xjava.security.IJCE_Traceable

tracing

Constructor Summary

FeedbackMode(boolean implBuffering, boolean implPadding, String provider)
Constructor for a Mode.

Method Summary

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, 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

Field Details

currentByte

protected int currentByte
Index into the ivBlock.


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.


length

protected int length
Size of the feedback register/queue/buffer.

Constructor Details

FeedbackMode

protected FeedbackMode(boolean implBuffering,
                       boolean implPadding,
                       String provider)

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.

Method Details

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 interface Mode

Parameters:
cipher - the underlying cipher object


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.


setInitializationVector

public void setInitializationVector(byte[] iv)
            throws 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.

Parameters:
iv - the initialization vector.