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Java > Open Source Codes > com > lowagie > text > pdf > crypto > ARCFOUREncryption


1 /*
2  * $Id: ARCFOUREncryption.java 2699 2007-04-19 12:19:40Z blowagie $
3  *
4  * Copyright 2006 Paulo Soares
5  *
6  * The contents of this file are subject to the Mozilla Public License Version 1.1
7  * (the "License"); you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at http://www.mozilla.org/MPL/
9  *
10  * Software distributed under the License is distributed on an "AS IS" basis,
11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12  * for the specific language governing rights and limitations under the License.
13  *
14  * The Original Code is 'iText, a free JAVA-PDF library'.
15  *
16  * The Initial Developer of the Original Code is Bruno Lowagie. Portions created by
17  * the Initial Developer are Copyright (C) 1999, 2000, 2001, 2002 by Bruno Lowagie.
18  * All Rights Reserved.
19  * Co-Developer of the code is Paulo Soares. Portions created by the Co-Developer
20  * are Copyright (C) 2000, 2001, 2002 by Paulo Soares. All Rights Reserved.
21  *
22  * Contributor(s): all the names of the contributors are added in the source code
23  * where applicable.
24  *
25  * Alternatively, the contents of this file may be used under the terms of the
26  * LGPL license (the "GNU LIBRARY GENERAL PUBLIC LICENSE"), in which case the
27  * provisions of LGPL are applicable instead of those above. If you wish to
28  * allow use of your version of this file only under the terms of the LGPL
29  * License and not to allow others to use your version of this file under
30  * the MPL, indicate your decision by deleting the provisions above and
31  * replace them with the notice and other provisions required by the LGPL.
32  * If you do not delete the provisions above, a recipient may use your version
33  * of this file under either the MPL or the GNU LIBRARY GENERAL PUBLIC LICENSE.
34  *
35  * This library is free software; you can redistribute it and/or modify it
36  * under the terms of the MPL as stated above or under the terms of the GNU
37  * Library General Public License as published by the Free Software Foundation;
38  * either version 2 of the License, or any later version.
39  *
40  * This library is distributed in the hope that it will be useful, but WITHOUT
41  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
42  * FOR A PARTICULAR PURPOSE. See the GNU Library general Public License for more
43  * details.
44  *
45  * If you didn't download this code from the following link, you should check if
46  * you aren't using an obsolete version:
47  * http://www.lowagie.com/iText/
48  */
49 package com.lowagie.text.pdf.crypto;
50
51 public class ARCFOUREncryption {
52     private byte state[] = new byte[256];
53     private int x;
54     private int y;
55
56     /** Creates a new instance of ARCFOUREncryption */
57     public ARCFOUREncryption() {
58     }
59     
60     public void prepareARCFOURKey(byte key[]) {
61         prepareARCFOURKey(key, 0, key.length);
62     }
63
64     public void prepareARCFOURKey(byte key[], int off, int len) {
65         int index1 = 0;
66         int index2 = 0;
67         for (int k = 0; k < 256; ++k)
68             state[k] = (byte)k;
69         x = 0;
70         y = 0;
71         byte tmp;
72         for (int k = 0; k < 256; ++k) {
73             index2 = (key[index1 + off] + state[k] + index2) & 255;
74             tmp = state[k];
75             state[k] = state[index2];
76             state[index2] = tmp;
77             index1 = (index1 + 1) % len;
78         }
79     }
80
81     public void encryptARCFOUR(byte dataIn[], int off, int len, byte dataOut[], int offOut) {
82         int length = len + off;
83         byte tmp;
84         for (int k = off; k < length; ++k) {
85             x = (x + 1) & 255;
86             y = (state[x] + y) & 255;
87             tmp = state[x];
88             state[x] = state[y];
89             state[y] = tmp;
90             dataOut[k - off + offOut] = (byte)(dataIn[k] ^ state[(state[x] + state[y]) & 255]);
91         }
92     }
93
94     public void encryptARCFOUR(byte data[], int off, int len) {
95         encryptARCFOUR(data, off, len, data, off);
96     }
97
98     public void encryptARCFOUR(byte dataIn[], byte dataOut[]) {
99         encryptARCFOUR(dataIn, 0, dataIn.length, dataOut, 0);
100     }
101
102     public void encryptARCFOUR(byte data[]) {
103         encryptARCFOUR(data, 0, data.length, data, 0);
104     }
105 }
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