using System;
/*
 * $Id: ARCFOUREncryption.cs 106 2009-12-07 12:23:50Z psoares33 $
 *
 * This file is part of the iText project.
 * Copyright (c) 1998-2012 1T3XT BVBA
 * 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 1T3XT,
 * 1T3XT 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,
 * you 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: sales@itextpdf.com
 */
namespace iTextSharp.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);
        }   
    }
}
