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iText, a free Java-PDF library
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/*
 * $Id: ARCFOUREncryption.java 6134 2013-12-23 13:15:14Z blowagie $
 *
 * This file is part of the iText (R) project.
 * Copyright (c) 1998-2014 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: [email protected]
 */
package com.itextpdf.text.pdf.crypto;

public class ARCFOUREncryption {
    private byte state[] = new byte[256];
    private int x;
    private int y;

    /** Creates a new instance of ARCFOUREncryption */
    public ARCFOUREncryption() {
    }
    
    public void prepareARCFOURKey(byte key[]) {
        prepareARCFOURKey(key, 0, key.length);
    }

    public void prepareARCFOURKey(byte key[], int off, int len) {
        int index1 = 0;
        int index2 = 0;
        for (int k = 0; k < 256; ++k)
            state[k] = (byte)k;
        x = 0;
        y = 0;
        byte tmp;
        for (int k = 0; k < 256; ++k) {
            index2 = (key[index1 + off] + state[k] + index2) & 255;
            tmp = state[k];
            state[k] = state[index2];
            state[index2] = tmp;
            index1 = (index1 + 1) % len;
        }
    }

    public void encryptARCFOUR(byte dataIn[], int off, int len, byte dataOut[], int offOut) {
        int length = len + off;
        byte tmp;
        for (int k = off; k < length; ++k) {
            x = (x + 1) & 255;
            y = (state[x] + y) & 255;
            tmp = state[x];
            state[x] = state[y];
            state[y] = tmp;
            dataOut[k - off + offOut] = (byte)(dataIn[k] ^ state[(state[x] + state[y]) & 255]);
        }
    }

    public void encryptARCFOUR(byte data[], int off, int len) {
        encryptARCFOUR(data, off, len, data, off);
    }

    public void encryptARCFOUR(byte dataIn[], byte dataOut[]) {
        encryptARCFOUR(dataIn, 0, dataIn.length, dataOut, 0);
    }

    public void encryptARCFOUR(byte data[]) {
        encryptARCFOUR(data, 0, data.length, data, 0);
    }   
}