StreamCipher.java

00001 // StreamCipher - a stream encryption template
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 // <A HREF="/resources/classes/Acme/Crypto/StreamCipher.java">Fetch the software.</A><BR>
00036 // <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
00037 // <P>
00038 // @see Cipher
00039 // @see BlockCipher
00040 // @see EncryptedOutputStream
00041 // @see EncryptedInputStream
00042 // @see Rc4Cipher
00043 
00044 public abstract class StreamCipher extends Cipher
00045     {
00046 
00048     public StreamCipher( int keySize )
00049         {
00050         super( keySize );
00051         }
00052 
00054     public abstract byte encrypt( byte clearText );
00055 
00057     public abstract byte decrypt( byte cipherText );
00058 
00060     public void encrypt( byte[] clearText, byte[] cipherText )
00061         {
00062         encrypt( clearText, 0, cipherText, 0, clearText.length );
00063         }
00064 
00066     public void decrypt( byte[] cipherText, byte[] clearText )
00067         {
00068         decrypt( cipherText, 0, clearText, 0, cipherText.length );
00069         }
00070 
00072     // The default implementation just calls encrypt(byte) repeatedly.
00073     // This can be overridden for speed.
00074     public void encrypt( byte[] clearText, int clearOff, byte[] cipherText, int cipherOff, int len )
00075         {
00076         for ( int i = 0; i < len; ++i )
00077             cipherText[cipherOff + i] = encrypt( clearText[clearOff + i] );
00078         }
00079 
00081     // The default implementation just calls decrypt(byte) repeatedly.
00082     // This can be overridden for speed.
00083     public void decrypt( byte[] cipherText, int cipherOff, byte[] clearText, int clearOff, int len )
00084         {
00085         for ( int i = 0; i < len; ++i )
00086             clearText[clearOff + i] = decrypt( cipherText[cipherOff + i] );
00087         }
00088 
00089     }

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