package gnu.crypto.mode;

// ----------------------------------------------------------------------------
// $Id: ECB.java,v 1.6 2005/10/06 04:24:17 rsdio 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
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// General Public License for more details.
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//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
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// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;
import gnu.crypto.cipher.IBlockCipher;

/**
 * <p>The implementation of the Electronic Codebook mode.</p>
 *
 * <p>The Electronic Codebook (ECB) mode is a confidentiality mode that is
 * defined as follows:</p>
 *
 * <ul>
 *    <li>ECB Encryption: C<sub>j</sub> = CIPH<sub>K</sub>(P<sub>j</sub>) for j = 1...n</li>
 *    <li>ECB Decryption: P<sub>j</sub> = CIPH<sup>-1</sup><sub>K</sub>(C<sub>j</sub>) for j = 1...n</li>
 * </ul>
 *
 * <p>In ECB encryption, the forward cipher function is applied directly, and
 * independently, to each block of the plaintext. The resulting sequence of
 * output blocks is the ciphertext.</p>
 *
 * <p>In ECB decryption, the inverse cipher function is applied directly, and
 * independently, to each block of the ciphertext. The resulting sequence of
 * output blocks is the plaintext.</p>
 *
 * <p>References:</p>
 *
 * <ol>
 *    <li><a href="http://csrc.nist.gov/encryption/modes/Recommendation/Modes01.pdf">
 *    Recommendation for Block Cipher Modes of Operation Methods and Techniques</a>,
 *    Morris Dworkin.</li>
 * </ol>
 *
 * @version $Revision: 1.6 $
 */
public class ECB extends BaseMode implements Cloneable {

   // Constants and variables
   // -------------------------------------------------------------------------

   // Constructor(s)
   // -------------------------------------------------------------------------

   /**
    * <p>Trivial package-private constructor for use by the Factory class.</p>
    *
    * @param underlyingCipher the underlying cipher implementation.
    * @param cipherBlockSize the underlying cipher block size to use.
    */
   ECB(IBlockCipher underlyingCipher, int cipherBlockSize) {
      super(Registry.ECB_MODE, underlyingCipher, cipherBlockSize);
   }

   /**
    * <p>Private constructor for cloning purposes.</p>
    *
    * @param that the mode to clone.
    */
   private ECB(ECB that) {
      this((IBlockCipher) that.cipher.clone(), that.cipherBlockSize);
   }

   // Class methods
   // -------------------------------------------------------------------------

   // Instance methods
   // -------------------------------------------------------------------------

   // java.lang.Cloneable interface implementation ----------------------------

   public Object clone() {
      return new ECB(this);
   }

   // Implementation of abstract methods in BaseMode --------------------------

   public void setup() {
      if (modeBlockSize != cipherBlockSize) {
         throw new IllegalArgumentException(IMode.MODE_BLOCK_SIZE);
      }
   }

   public void teardown() {
   }

   public void encryptBlock(byte[] in, int i, byte[] out, int o) {
      cipher.encryptBlock(in, i, out, o);
   }

   public void decryptBlock(byte[] in, int i, byte[] out, int o) {
      cipher.decryptBlock(in, i, out, o);
   }
}