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NullCipher.java

00001 // NullCipher - the null encryption method
00002 //
00003 // Copyright (C) 1996 by Jef Poskanzer <jef@acme.com>.  All rights reserved.
00004 //
00005 // Redistribution and use in source and binary forms, with or without
00006 // modification, are permitted provided that the following conditions
00007 // are met:
00008 // 1. Redistributions of source code must retain the above copyright
00009 //    notice, this list of conditions and the following disclaimer.
00010 // 2. Redistributions in binary form must reproduce the above copyright
00011 //    notice, this list of conditions and the following disclaimer in the
00012 //    documentation and/or other materials provided with the distribution.
00013 //
00014 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
00015 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00016 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00017 // ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
00018 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00019 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00020 // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00021 // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00022 // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00023 // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00024 // SUCH DAMAGE.
00025 //
00026 // Visit the ACME Labs Java page for up-to-date versions of this and other
00027 // fine Java utilities: http://www.acme.com/java/
00028 
00029 package Acme.Crypto;
00030 
00031 import java.io.*;
00032 
00034 // <P>
00035 // This is a block cipher that just copies input to output, unmodified.
00036 // It's mostly for testing.  However, using the null cipher in CBC mode,
00037 // for example via EncryptedOutputStream and EncryptedInputStream, turns
00038 // out to hash things up enough to protect against casual inspection.
00039 // There may be applications where this is appropriate.
00040 // <P>
00041 // <A HREF="/resources/classes/Acme/Crypto/NullCipher.java">Fetch the software.</A><BR>
00042 // <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
00043 // <P>
00044 // @see EncryptedOutputStream
00045 // @see EncryptedInputStream
00046 
00047 public class NullCipher extends BlockCipher
00048     {
00049 
00051     public NullCipher()
00052         {
00053         super( 0, 8 );
00054         }
00055 
00056 
00057     // Key routines.
00058 
00060     public void setKey( byte[] key )
00061         {
00062         throw new InternalError( "NullCipher does not need a key" );
00063         }
00064 
00065 
00066     // Block encryption routines.
00067 
00069     public void encrypt( byte[] clearText, int clearOff, byte[] cipherText, int cipherOff )
00070         {
00071         copyBlock( clearText, clearOff, cipherText, cipherOff, blockSize );
00072         }
00073 
00075     public void decrypt( byte[] cipherText, int cipherOff, byte[] clearText, int clearOff )
00076         {
00077         copyBlock( cipherText, cipherOff, clearText, clearOff, blockSize );
00078         }
00079 
00080     }

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