/* ====================================================================
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for Additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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==================================================================== */
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namespace HH.WMS.Utils.NPOI.HSSF.Record.Crypto
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{
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using System;
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using System.Text;
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using HH.WMS.Utils.NPOI.Util;
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/**
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* Simple implementation of the alleged RC4 algorithm.
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*
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* Inspired by <A HREF="http://en.wikipedia.org/wiki/RC4">wikipedia's RC4 article</A>
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*
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* @author Josh Micich
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*/
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internal class RC4
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{
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private int _i, _j;
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private byte[] _s = new byte[256];
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public RC4(byte[] key)
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{
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int key_length = key.Length;
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for (int i = 0; i < 256; i++)
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_s[i] = (byte)i;
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for (int i = 0, j = 0; i < 256; i++)
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{
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byte temp;
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j = (j + key[i % key_length] + _s[i]) & 255;
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temp = _s[i];
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_s[i] = _s[j];
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_s[j] = temp;
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}
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_i = 0;
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_j = 0;
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}
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public byte Output()
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{
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byte temp;
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_i = (_i + 1) & 255;
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_j = (_j + _s[_i]) & 255;
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temp = _s[_i];
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_s[_i] = _s[_j];
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_s[_j] = temp;
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return _s[(_s[_i] + _s[_j]) & 255];
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}
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public void Encrypt(byte[] in1)
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{
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for (int i = 0; i < in1.Length; i++)
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{
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in1[i] = (byte)(in1[i] ^ Output());
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}
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}
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public void Encrypt(byte[] in1, int OffSet, int len)
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{
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int end = OffSet + len;
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for (int i = OffSet; i < end; i++)
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{
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in1[i] = (byte)(in1[i] ^ Output());
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}
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}
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public override String ToString()
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{
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StringBuilder sb = new StringBuilder();
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sb.Append(GetType().Name).Append(" [");
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sb.Append("i=").Append(_i);
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sb.Append(" j=").Append(_j);
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sb.Append("]");
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sb.Append("\n");
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sb.Append(HexDump.Dump(_s, 0, 0));
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return sb.ToString();
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}
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}
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}
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