gnu.crypto.mode.IMode Maven / Gradle / Ivy
package gnu.crypto.mode;
// ----------------------------------------------------------------------------
// $Id: IMode.java,v 1.4 2002/11/07 17:17:45 raif Exp $
//
// Copyright (C) 2001, 2002, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 59 Temple Place - Suite 330,
// Boston, MA 02111-1307
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import gnu.crypto.cipher.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:
*
*
* - Depending on the specifications of the mode, the block size may be
* different that that of the underlying cipher.
*
* - While some modes of operations allow operations on block sizes that
* can be 1-bit long, this library will only deal with sizes that are
* multiple of 8 bits. This is because the byte is the smallest,
* easy to handle, primitive type in Java.
*
* - Some modes need an Initialisation Vector (IV) to be properly
* initialised.
*
*
* Possible additional initialisation values for an instance of that type
* are:
*
*
* - The block size in which to operate this mode instance. This
* value is optional, if unspecified, the underlying block cipher's
* configured block size shall be used.
*
* - Whether this mode will be used for encryption or decryption. This
* value is mandatory and should be included in the initialisation
* parameters. If it isn't, a {@link java.lang.IllegalStateException} will
* be thrown if any method, other than
reset() is invoked on the
* instance.
*
* - The byte array containing the initialisation vector, if
* required by this type of mode.
*
*
* @version $Revision: 1.4 $
*/
public interface IMode extends IBlockCipher {
// Constants
// -------------------------------------------------------------------------
/**
* Property name of the state in which to operate this mode. The value
* associated to this property name is taken to be an {@link Integer} which
* value is either ENCRYPTION or DECRYPTION.
*/
String STATE = "gnu.crypto.mode.state";
/**
* Property name of the block size in which to operate this mode. The
* value associated with this property name is taken to be an {@link 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.
*/
String MODE_BLOCK_SIZE = "gnu.crypto.mode.block.size";
/**
* 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.
*/
String IV = "gnu.crypto.mode.iv";
/**
* Constant indicating the instance is being used for encryption.
*/
int ENCRYPTION = 1;
/**
* Constant indicating the instance is being used for decryption.
*/
int DECRYPTION = 2;
// Methods
// -------------------------------------------------------------------------
/**
* A convenience method. Effectively invokes the encryptBlock()
* or decryptBlock() method depending on the operational state
* of the instance.
*
* @param in the plaintext.
* @param inOffset index of in from which to start considering
* data.
* @param out the ciphertext.
* @param outOffset index of out from which to store result.
* @exception IllegalStateException if the instance is not initialised.
*/
void update(byte[] in, int inOffset, byte[] out, int outOffset)
throws IllegalStateException;
}