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Java > Open Source Codes > Acme > Crypto > Cipher


1 // Cipher - an encryption template
2 //
3 // Copyright (C) 1996 by Jef Poskanzer <jef@acme.com>. All rights reserved.
4 //
5 // Redistribution and use in source and binary forms, with or without
6 // modification, are permitted provided that the following conditions
7 // are met:
8 // 1. Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 // 2. Redistributions in binary form must reproduce the above copyright
11 // notice, this list of conditions and the following disclaimer in the
12 // documentation and/or other materials provided with the distribution.
13 //
14 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 // ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 // SUCH DAMAGE.
25 //
26 // Visit the ACME Labs Java page for up-to-date versions of this and other
27 // fine Java utilities: http://www.acme.com/java/
28
29 package Acme.Crypto;
30
31 import java.io.*;
32
33 /// An encryption template.
34 // <P>
35 // <A HREF="../../../resources/classes/Acme/Crypto/Cipher.java">Fetch the software.</A><BR>
36 // <A HREF="../../../resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
37 // <P>
38 // @see StreamCipher
39 // @see BlockCipher
40 // @see EncryptedOutputStream
41 // @see EncryptedInputStream
42
43 public abstract class Cipher extends CryptoUtils
44     {
45
46     /// Constructor.
47 public Cipher( int keySize )
48     {
49     this.keySize = keySize;
50     }
51
52     /// How big a key is. Keyless ciphers use 0. Variable-length-key ciphers
53 // also use 0.
54 public int keySize;
55
56     /// Return how big a key is.
57 public int keySize()
58     {
59     return keySize;
60     }
61
62     /// Set the key from a block of bytes.
63 public abstract void setKey( byte[] key );
64
65
66     // Utility routines.
67
68     /// Utility routine to set the key from a string.
69 public void setKey( String JavaDoc keyStr )
70     {
71     setKey( makeKey( keyStr ) );
72     }
73
74     /// Utility routine to turn a string into a key of the right length.
75 public byte[] makeKey( String JavaDoc keyStr )
76     {
77         byte[] key;
78     if ( keySize == 0 )
79         key = new byte[keyStr.length()];
80     else
81         key = new byte[keySize];
82         int i, j;
83
84         for ( j = 0; j < key.length; ++j )
85             key[j] = 0;
86
87         for ( i = 0, j = 0; i < keyStr.length(); ++i, j = (j+1) % key.length )
88             key[j] ^= (byte) keyStr.charAt( i );
89
90     return key;
91     }
92
93     }
94
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