gnu.crypto.mode

Interface IMode

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: 1.5 $

Field Summary
intDECRYPTION

Constant indicating the instance is being used for decryption.

intENCRYPTION

Constant indicating the instance is being used for encryption.

StringIV

Property name of the initialisation vector to use, if required, with this instance.

StringMODE_BLOCK_SIZE

Property name of the block size in which to operate this mode.

StringSTATE

Property name of the state in which to operate this mode.

Method Summary
voidupdate(byte[] in, int inOffset, byte[] out, int outOffset)

A convenience method.

Field Detail

DECRYPTION

public int DECRYPTION

Constant indicating the instance is being used for decryption.

ENCRYPTION

public int ENCRYPTION

Constant indicating the instance is being used for encryption.

IV

public 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 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 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 Detail

update

public void update(byte[] in, int inOffset, byte[] out, int outOffset)

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.

Throws: IllegalStateException if the instance is not initialised.

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