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


1 /*
2  * $Id: IVGenerator.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 /**
52  * An initialization vector generator for a CBC block encryption. It's a random generator based on ARCFOUR.
53  * @author Paulo Soares (psoares@consiste.pt)
54  */
55 public class IVGenerator {
56     
57     private static ARCFOUREncryption arcfour;
58     
59     static {
60         arcfour = new ARCFOUREncryption();
61         long time = System.currentTimeMillis();
62         long mem = Runtime.getRuntime().freeMemory();
63         String JavaDoc s = time + "+" + mem;
64         arcfour.prepareARCFOURKey(s.getBytes());
65     }
66     
67     /** Creates a new instance of IVGenerator */
68     private IVGenerator() {
69     }
70     
71     /**
72      * Gets a 16 byte random initialization vector.
73      * @return a 16 byte random initialization vector
74      */
75     public static byte[] getIV() {
76         return getIV(16);
77     }
78     
79     /**
80      * Gets a random initialization vector.
81      * @param len the length of the initialization vector
82      * @return a random initialization vector
83      */
84     public static byte[] getIV(int len) {
85         byte[] b = new byte[len];
86         synchronized (arcfour) {
87             arcfour.encryptARCFOUR(b);
88         }
89         return b;
90     }
91 }
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