gnu.crypto.mode

Interface IMode

All Superinterfaces:
Cloneable, IBlockCipher
Known Implementing Classes:
BaseMode, CBC, CFB, CTR, ECB, ICM, OFB

public interface IMode
extends IBlockCipher

The basic visible methods of any block cipher mode.

Block ciphers encrypt plaintext in fixed size n-bit blocks. For messages larger than n bits, the simplest approach is to segment the message into n-bit blocks and process (encrypt and/or decrypt) each one separately (Electronic Codebook or ECB mode). But this approach has disadvantages in most applications. The block cipher modes of operations are one way of working around those disadvantages.

A Mode always employs an underlying block cipher for processing its input. For all intents and purposes, a Mode appears to behave as any other block cipher with the following differences:

Possible additional initialisation values for an instance of that type are:

Version:
$Revision: 1.4 $

Field Summary

static int
DECRYPTION
Constant indicating the instance is being used for decryption.
static int
ENCRYPTION
Constant indicating the instance is being used for encryption.
static String
IV
Property name of the initialisation vector to use, if required, with this instance.
static String
MODE_BLOCK_SIZE
Property name of the block size in which to operate this mode.
static String
STATE
Property name of the state in which to operate this mode.

Fields inherited from interface gnu.crypto.cipher.IBlockCipher

CIPHER_BLOCK_SIZE, KEY_MATERIAL

Method Summary

void
update(byte[] in, int inOffset, byte[] out, int outOffset)
A convenience method.

Methods inherited from interface gnu.crypto.cipher.IBlockCipher

blockSizes, clone, currentBlockSize, decryptBlock, defaultBlockSize, defaultKeySize, encryptBlock, init, keySizes, name, reset, selfTest

Field Details

DECRYPTION

public static final int DECRYPTION
Constant indicating the instance is being used for decryption.

Field Value:
2


ENCRYPTION

public static final int ENCRYPTION
Constant indicating the instance is being used for encryption.

Field Value:
1


IV

public static final String IV
Property name of the initialisation vector to use, if required, with this instance. The value associated with this property name is taken to be a byte array. If the concrete instance needs such a parameter, and it has not been specified as part of the initialissation parameters, an all-zero byte array of the appropriate size shall be used.


MODE_BLOCK_SIZE

public static final String MODE_BLOCK_SIZE
Property name of the block size in which to operate this mode. The value associated with this property name is taken to be an Integer. If it is not specified, the value of the block size of the underlying block cipher, used to construct the mode instance, shall be used.


STATE

public static final String STATE
Property name of the state in which to operate this mode. The value associated to this property name is taken to be an Integer which value is either ENCRYPTION or DECRYPTION.

Method Details

update

public void update(byte[] in,
                   int inOffset,
                   byte[] out,
                   int outOffset)
            throws IllegalStateException
A convenience method. Effectively invokes the encryptBlock() or decryptBlock() method depending on the operational state of the instance.

Parameters:
in - the plaintext.
inOffset - index of in from which to start considering data.
out - the ciphertext.
outOffset - index of out from which to store result.


Copyright © 2001, 2002, 2003 Free Software Foundation, Inc. All Rights Reserved.