001/*
002 * $Id: IVGenerator.java 4784 2011-03-15 08:33:00Z blowagie $
003 *
004 * This file is part of the iText (R) project.
005 * Copyright (c) 1998-2011 1T3XT BVBA
006 * Authors: Bruno Lowagie, Paulo Soares, et al.
007 *
008 * This program is free software; you can redistribute it and/or modify
009 * it under the terms of the GNU Affero General Public License version 3
010 * as published by the Free Software Foundation with the addition of the
011 * following permission added to Section 15 as permitted in Section 7(a):
012 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY 1T3XT,
013 * 1T3XT DISCLAIMS THE WARRANTY OF NON INFRINGEMENT OF THIRD PARTY RIGHTS.
014 *
015 * This program is distributed in the hope that it will be useful, but
016 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
017 * or FITNESS FOR A PARTICULAR PURPOSE.
018 * See the GNU Affero General Public License for more details.
019 * You should have received a copy of the GNU Affero General Public License
020 * along with this program; if not, see http://www.gnu.org/licenses or write to
021 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
022 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
023 * http://itextpdf.com/terms-of-use/
024 *
025 * The interactive user interfaces in modified source and object code versions
026 * of this program must display Appropriate Legal Notices, as required under
027 * Section 5 of the GNU Affero General Public License.
028 *
029 * In accordance with Section 7(b) of the GNU Affero General Public License,
030 * a covered work must retain the producer line in every PDF that is created
031 * or manipulated using iText.
032 *
033 * You can be released from the requirements of the license by purchasing
034 * a commercial license. Buying such a license is mandatory as soon as you
035 * develop commercial activities involving the iText software without
036 * disclosing the source code of your own applications.
037 * These activities include: offering paid services to customers as an ASP,
038 * serving PDFs on the fly in a web application, shipping iText with a closed
039 * source product.
040 *
041 * For more information, please contact iText Software Corp. at this
042 * address: sales@itextpdf.com
043 */
044package com.itextpdf.text.pdf.crypto;
045
046/**
047 * An initialization vector generator for a CBC block encryption. It's a random generator based on ARCFOUR.
048 * @author Paulo Soares
049 */
050public final class IVGenerator {
051    
052    private static ARCFOUREncryption arcfour;
053    
054    static {
055        arcfour = new ARCFOUREncryption();
056        long time = System.currentTimeMillis();
057        long mem = Runtime.getRuntime().freeMemory();
058        String s = time + "+" + mem;
059        arcfour.prepareARCFOURKey(s.getBytes());
060    }
061    
062    /** Creates a new instance of IVGenerator */
063    private IVGenerator() {
064    }
065    
066    /**
067     * Gets a 16 byte random initialization vector.
068     * @return a 16 byte random initialization vector
069     */
070    public static byte[] getIV() {
071        return getIV(16);
072    }
073    
074    /**
075     * Gets a random initialization vector.
076     * @param len the length of the initialization vector
077     * @return a random initialization vector
078     */
079    public static byte[] getIV(int len) {
080        byte[] b = new byte[len];
081        synchronized (arcfour) {
082            arcfour.encryptARCFOUR(b);
083        }
084        return b;
085    }    
086}