//
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// PkzipClassic encryption
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//
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// Copyright 2004 John Reilly
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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//
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// Linking this library statically or dynamically with other modules is
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// making a combined work based on this library. Thus, the terms and
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// conditions of the GNU General Public License cover the whole
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// combination.
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//
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// As a special exception, the copyright holders of this library give you
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// permission to link this library with independent modules to produce an
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// executable, regardless of the license terms of these independent
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// modules, and to copy and distribute the resulting executable under
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// terms of your choice, provided that you also meet, for each linked
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// independent module, the terms and conditions of the license of that
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// module. An independent module is a module which is not derived from
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// or based on this library. If you modify this library, you may extend
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// this exception to your version of the library, but you are not
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// obligated to do so. If you do not wish to do so, delete this
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// exception statement from your version.
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//
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#if !NETCF_1_0
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using System;
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using System.Security.Cryptography;
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using ICSharpCode.SharpZipLib.Checksums;
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namespace ICSharpCode.SharpZipLib.Encryption
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{
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/// <summary>
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/// PkzipClassic embodies the classic or original encryption facilities used in Pkzip archives.
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/// While it has been superceded by more recent and more powerful algorithms, its still in use and
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/// is viable for preventing casual snooping
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/// </summary>
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public abstract class PkzipClassic : SymmetricAlgorithm
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{
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/// <summary>
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/// Generates new encryption keys based on given seed
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/// </summary>
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/// <param name="seed">The seed value to initialise keys with.</param>
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/// <returns>A new key value.</returns>
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static public byte[] GenerateKeys(byte[] seed)
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{
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if ( seed == null ) {
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throw new ArgumentNullException("seed");
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}
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if ( seed.Length == 0 ) {
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throw new ArgumentException("Length is zero", "seed");
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}
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uint[] newKeys = new uint[] {
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0x12345678,
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0x23456789,
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0x34567890
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};
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for (int i = 0; i < seed.Length; ++i) {
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newKeys[0] = Crc32.ComputeCrc32(newKeys[0], seed[i]);
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newKeys[1] = newKeys[1] + (byte)newKeys[0];
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newKeys[1] = newKeys[1] * 134775813 + 1;
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newKeys[2] = Crc32.ComputeCrc32(newKeys[2], (byte)(newKeys[1] >> 24));
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}
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byte[] result = new byte[12];
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result[0] = (byte)(newKeys[0] & 0xff);
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result[1] = (byte)((newKeys[0] >> 8) & 0xff);
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result[2] = (byte)((newKeys[0] >> 16) & 0xff);
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result[3] = (byte)((newKeys[0] >> 24) & 0xff);
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result[4] = (byte)(newKeys[1] & 0xff);
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result[5] = (byte)((newKeys[1] >> 8) & 0xff);
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result[6] = (byte)((newKeys[1] >> 16) & 0xff);
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result[7] = (byte)((newKeys[1] >> 24) & 0xff);
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result[8] = (byte)(newKeys[2] & 0xff);
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result[9] = (byte)((newKeys[2] >> 8) & 0xff);
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result[10] = (byte)((newKeys[2] >> 16) & 0xff);
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result[11] = (byte)((newKeys[2] >> 24) & 0xff);
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return result;
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}
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}
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/// <summary>
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/// PkzipClassicCryptoBase provides the low level facilities for encryption
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/// and decryption using the PkzipClassic algorithm.
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/// </summary>
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class PkzipClassicCryptoBase
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{
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/// <summary>
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/// Transform a single byte
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/// </summary>
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/// <returns>
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/// The transformed value
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/// </returns>
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protected byte TransformByte()
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{
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uint temp = ((keys[2] & 0xFFFF) | 2);
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return (byte)((temp * (temp ^ 1)) >> 8);
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}
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/// <summary>
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/// Set the key schedule for encryption/decryption.
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/// </summary>
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/// <param name="keyData">The data use to set the keys from.</param>
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protected void SetKeys(byte[] keyData)
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{
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if ( keyData == null ) {
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throw new ArgumentNullException("keyData");
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}
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if ( keyData.Length != 12 ) {
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throw new InvalidOperationException("Key length is not valid");
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}
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keys = new uint[3];
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keys[0] = (uint)((keyData[3] << 24) | (keyData[2] << 16) | (keyData[1] << 8) | keyData[0]);
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keys[1] = (uint)((keyData[7] << 24) | (keyData[6] << 16) | (keyData[5] << 8) | keyData[4]);
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keys[2] = (uint)((keyData[11] << 24) | (keyData[10] << 16) | (keyData[9] << 8) | keyData[8]);
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}
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/// <summary>
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/// Update encryption keys
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/// </summary>
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protected void UpdateKeys(byte ch)
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{
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keys[0] = Crc32.ComputeCrc32(keys[0], ch);
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keys[1] = keys[1] + (byte)keys[0];
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keys[1] = keys[1] * 134775813 + 1;
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keys[2] = Crc32.ComputeCrc32(keys[2], (byte)(keys[1] >> 24));
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}
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/// <summary>
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/// Reset the internal state.
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/// </summary>
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protected void Reset()
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{
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keys[0] = 0;
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keys[1] = 0;
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keys[2] = 0;
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}
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#region Instance Fields
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uint[] keys;
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#endregion
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}
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/// <summary>
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/// PkzipClassic CryptoTransform for encryption.
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/// </summary>
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class PkzipClassicEncryptCryptoTransform : PkzipClassicCryptoBase, ICryptoTransform
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{
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/// <summary>
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/// Initialise a new instance of <see cref="PkzipClassicEncryptCryptoTransform"></see>
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/// </summary>
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/// <param name="keyBlock">The key block to use.</param>
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internal PkzipClassicEncryptCryptoTransform(byte[] keyBlock)
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{
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SetKeys(keyBlock);
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}
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#region ICryptoTransform Members
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/// <summary>
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/// Transforms the specified region of the specified byte array.
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/// </summary>
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/// <param name="inputBuffer">The input for which to compute the transform.</param>
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/// <param name="inputOffset">The offset into the byte array from which to begin using data.</param>
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/// <param name="inputCount">The number of bytes in the byte array to use as data.</param>
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/// <returns>The computed transform.</returns>
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public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
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{
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byte[] result = new byte[inputCount];
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TransformBlock(inputBuffer, inputOffset, inputCount, result, 0);
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return result;
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}
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/// <summary>
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/// Transforms the specified region of the input byte array and copies
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/// the resulting transform to the specified region of the output byte array.
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/// </summary>
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/// <param name="inputBuffer">The input for which to compute the transform.</param>
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/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
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/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
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/// <param name="outputBuffer">The output to which to write the transform.</param>
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/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
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/// <returns>The number of bytes written.</returns>
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public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
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{
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for (int i = inputOffset; i < inputOffset + inputCount; ++i) {
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byte oldbyte = inputBuffer[i];
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outputBuffer[outputOffset++] = (byte)(inputBuffer[i] ^ TransformByte());
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UpdateKeys(oldbyte);
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}
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return inputCount;
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}
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/// <summary>
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/// Gets a value indicating whether the current transform can be reused.
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/// </summary>
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public bool CanReuseTransform
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{
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get {
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return true;
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}
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}
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/// <summary>
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/// Gets the size of the input data blocks in bytes.
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/// </summary>
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public int InputBlockSize
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{
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get {
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return 1;
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}
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}
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/// <summary>
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/// Gets the size of the output data blocks in bytes.
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/// </summary>
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public int OutputBlockSize
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{
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get {
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return 1;
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}
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}
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/// <summary>
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/// Gets a value indicating whether multiple blocks can be transformed.
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/// </summary>
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public bool CanTransformMultipleBlocks
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{
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get {
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return true;
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}
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}
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#endregion
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#region IDisposable Members
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/// <summary>
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/// Cleanup internal state.
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/// </summary>
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public void Dispose()
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{
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Reset();
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}
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#endregion
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}
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/// <summary>
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/// PkzipClassic CryptoTransform for decryption.
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/// </summary>
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class PkzipClassicDecryptCryptoTransform : PkzipClassicCryptoBase, ICryptoTransform
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{
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/// <summary>
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/// Initialise a new instance of <see cref="PkzipClassicDecryptCryptoTransform"></see>.
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/// </summary>
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/// <param name="keyBlock">The key block to decrypt with.</param>
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internal PkzipClassicDecryptCryptoTransform(byte[] keyBlock)
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{
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SetKeys(keyBlock);
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}
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#region ICryptoTransform Members
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/// <summary>
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/// Transforms the specified region of the specified byte array.
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/// </summary>
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/// <param name="inputBuffer">The input for which to compute the transform.</param>
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/// <param name="inputOffset">The offset into the byte array from which to begin using data.</param>
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/// <param name="inputCount">The number of bytes in the byte array to use as data.</param>
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/// <returns>The computed transform.</returns>
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public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
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{
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byte[] result = new byte[inputCount];
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TransformBlock(inputBuffer, inputOffset, inputCount, result, 0);
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return result;
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}
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/// <summary>
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/// Transforms the specified region of the input byte array and copies
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/// the resulting transform to the specified region of the output byte array.
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/// </summary>
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/// <param name="inputBuffer">The input for which to compute the transform.</param>
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/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
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/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
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/// <param name="outputBuffer">The output to which to write the transform.</param>
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/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
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/// <returns>The number of bytes written.</returns>
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public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
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{
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for (int i = inputOffset; i < inputOffset + inputCount; ++i) {
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byte newByte = (byte)(inputBuffer[i] ^ TransformByte());
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outputBuffer[outputOffset++] = newByte;
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UpdateKeys(newByte);
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}
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return inputCount;
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}
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/// <summary>
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/// Gets a value indicating whether the current transform can be reused.
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/// </summary>
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public bool CanReuseTransform
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{
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get {
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return true;
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}
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}
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/// <summary>
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/// Gets the size of the input data blocks in bytes.
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/// </summary>
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public int InputBlockSize
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{
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get {
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return 1;
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}
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}
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/// <summary>
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/// Gets the size of the output data blocks in bytes.
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/// </summary>
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public int OutputBlockSize
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{
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get {
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return 1;
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}
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}
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/// <summary>
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/// Gets a value indicating whether multiple blocks can be transformed.
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/// </summary>
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public bool CanTransformMultipleBlocks
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{
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get {
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return true;
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}
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}
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#endregion
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#region IDisposable Members
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/// <summary>
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/// Cleanup internal state.
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/// </summary>
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public void Dispose()
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{
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Reset();
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}
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#endregion
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}
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/// <summary>
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/// Defines a wrapper object to access the Pkzip algorithm.
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/// This class cannot be inherited.
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/// </summary>
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public sealed class PkzipClassicManaged : PkzipClassic
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{
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/// <summary>
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/// Get / set the applicable block size in bits.
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/// </summary>
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/// <remarks>The only valid block size is 8.</remarks>
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public override int BlockSize
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{
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get {
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return 8;
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}
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set {
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if (value != 8) {
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throw new CryptographicException("Block size is invalid");
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}
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}
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}
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/// <summary>
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/// Get an array of legal <see cref="KeySizes">key sizes.</see>
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/// </summary>
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public override KeySizes[] LegalKeySizes
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{
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get {
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KeySizes[] keySizes = new KeySizes[1];
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keySizes[0] = new KeySizes(12 * 8, 12 * 8, 0);
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return keySizes;
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}
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}
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/// <summary>
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/// Generate an initial vector.
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/// </summary>
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public override void GenerateIV()
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{
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// Do nothing.
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}
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/// <summary>
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/// Get an array of legal <see cref="KeySizes">block sizes</see>.
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/// </summary>
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public override KeySizes[] LegalBlockSizes
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{
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get {
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KeySizes[] keySizes = new KeySizes[1];
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keySizes[0] = new KeySizes(1 * 8, 1 * 8, 0);
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return keySizes;
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}
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}
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/// <summary>
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/// Get / set the key value applicable.
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/// </summary>
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public override byte[] Key
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{
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get {
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if ( key_ == null ) {
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GenerateKey();
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}
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return (byte[]) key_.Clone();
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}
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set {
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if ( value == null ) {
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throw new ArgumentNullException("value");
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}
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if ( value.Length != 12 ) {
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throw new CryptographicException("Key size is illegal");
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}
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key_ = (byte[]) value.Clone();
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}
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}
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/// <summary>
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/// Generate a new random key.
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/// </summary>
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public override void GenerateKey()
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{
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key_ = new byte[12];
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Random rnd = new Random();
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rnd.NextBytes(key_);
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}
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/// <summary>
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/// Create an encryptor.
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/// </summary>
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/// <param name="rgbKey">The key to use for this encryptor.</param>
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/// <param name="rgbIV">Initialisation vector for the new encryptor.</param>
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/// <returns>Returns a new PkzipClassic encryptor</returns>
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public override ICryptoTransform CreateEncryptor(
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byte[] rgbKey,
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byte[] rgbIV)
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{
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key_ = rgbKey;
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return new PkzipClassicEncryptCryptoTransform(Key);
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}
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/// <summary>
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/// Create a decryptor.
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/// </summary>
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/// <param name="rgbKey">Keys to use for this new decryptor.</param>
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/// <param name="rgbIV">Initialisation vector for the new decryptor.</param>
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/// <returns>Returns a new decryptor.</returns>
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public override ICryptoTransform CreateDecryptor(
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byte[] rgbKey,
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byte[] rgbIV)
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{
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key_ = rgbKey;
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return new PkzipClassicDecryptCryptoTransform(Key);
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}
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#region Instance Fields
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byte[] key_;
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#endregion
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}
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}
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#endif
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