233 lines
6.1 KiB
C#
233 lines
6.1 KiB
C#
/*
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KeePass Password Safe - The Open-Source Password Manager
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Copyright (C) 2003-2016 Dominik Reichl <dominik.reichl@t-online.de>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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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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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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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using System;
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using System.Diagnostics;
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#if !KeePassUAP
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using System.Security.Cryptography;
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#endif
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using KeePassLib.Cryptography.Cipher;
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using KeePassLib.Utility;
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namespace KeePassLib.Cryptography
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{
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/// <summary>
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/// Algorithms supported by <c>CryptoRandomStream</c>.
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/// </summary>
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public enum CrsAlgorithm
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{
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/// <summary>
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/// Not supported.
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/// </summary>
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Null = 0,
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/// <summary>
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/// A variant of the ARCFour algorithm (RC4 incompatible).
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/// Insecure; for backward compatibility only.
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/// </summary>
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ArcFourVariant = 1,
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/// <summary>
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/// Salsa20 stream cipher algorithm.
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/// </summary>
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Salsa20 = 2,
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/// <summary>
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/// ChaCha20 stream cipher algorithm.
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/// </summary>
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ChaCha20 = 3,
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Count = 4
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}
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/// <summary>
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/// A random stream class. The class is initialized using random
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/// bytes provided by the caller. The produced stream has random
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/// properties, but for the same seed always the same stream
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/// is produced, i.e. this class can be used as stream cipher.
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/// </summary>
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public sealed class CryptoRandomStream
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{
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private readonly CrsAlgorithm m_crsAlgorithm;
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private byte[] m_pbState = null;
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private byte m_i = 0;
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private byte m_j = 0;
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private Salsa20Cipher m_salsa20 = null;
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private ChaCha20Cipher m_chacha20 = null;
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/// <summary>
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/// Construct a new cryptographically secure random stream object.
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/// </summary>
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/// <param name="a">Algorithm to use.</param>
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/// <param name="pbKey">Initialization key. Must not be <c>null</c> and
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/// must contain at least 1 byte.</param>
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public CryptoRandomStream(CrsAlgorithm a, byte[] pbKey)
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{
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if(pbKey == null) { Debug.Assert(false); throw new ArgumentNullException("pbKey"); }
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int cbKey = pbKey.Length;
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if(cbKey <= 0)
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{
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Debug.Assert(false); // Need at least one byte
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throw new ArgumentOutOfRangeException("pbKey");
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}
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m_crsAlgorithm = a;
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if(a == CrsAlgorithm.ChaCha20)
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{
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byte[] pbKey32 = new byte[32];
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byte[] pbIV12 = new byte[12];
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using(SHA512Managed h = new SHA512Managed())
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{
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byte[] pbHash = h.ComputeHash(pbKey);
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Array.Copy(pbHash, pbKey32, 32);
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Array.Copy(pbHash, 32, pbIV12, 0, 12);
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MemUtil.ZeroByteArray(pbHash);
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}
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m_chacha20 = new ChaCha20Cipher(pbKey32, pbIV12, true);
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}
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else if(a == CrsAlgorithm.Salsa20)
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{
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byte[] pbKey32 = CryptoUtil.HashSha256(pbKey);
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byte[] pbIV8 = new byte[8] { 0xE8, 0x30, 0x09, 0x4B,
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0x97, 0x20, 0x5D, 0x2A }; // Unique constant
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m_salsa20 = new Salsa20Cipher(pbKey32, pbIV8);
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}
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else if(a == CrsAlgorithm.ArcFourVariant)
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{
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// Fill the state linearly
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m_pbState = new byte[256];
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for(int w = 0; w < 256; ++w) m_pbState[w] = (byte)w;
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unchecked
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{
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byte j = 0, t;
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int inxKey = 0;
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for(int w = 0; w < 256; ++w) // Key setup
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{
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j += (byte)(m_pbState[w] + pbKey[inxKey]);
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t = m_pbState[0]; // Swap entries
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m_pbState[0] = m_pbState[j];
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m_pbState[j] = t;
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++inxKey;
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if(inxKey >= cbKey) inxKey = 0;
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}
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}
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GetRandomBytes(512); // Increases security, see cryptanalysis
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}
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else // Unknown algorithm
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{
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Debug.Assert(false);
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throw new ArgumentOutOfRangeException("a");
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}
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}
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/// <summary>
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/// Get <paramref name="uRequestedCount" /> random bytes.
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/// </summary>
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/// <param name="uRequestedCount">Number of random bytes to retrieve.</param>
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/// <returns>Returns <paramref name="uRequestedCount" /> random bytes.</returns>
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public byte[] GetRandomBytes(uint uRequestedCount)
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{
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if(uRequestedCount == 0) return MemUtil.EmptyByteArray;
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if(uRequestedCount > (uint)int.MaxValue)
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throw new ArgumentOutOfRangeException("uRequestedCount");
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int cb = (int)uRequestedCount;
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byte[] pbRet = new byte[cb];
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if(m_crsAlgorithm == CrsAlgorithm.ChaCha20)
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m_chacha20.Encrypt(pbRet, 0, cb);
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else if(m_crsAlgorithm == CrsAlgorithm.Salsa20)
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m_salsa20.Encrypt(pbRet, 0, cb);
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else if(m_crsAlgorithm == CrsAlgorithm.ArcFourVariant)
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{
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unchecked
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{
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for(int w = 0; w < cb; ++w)
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{
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++m_i;
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m_j += m_pbState[m_i];
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byte t = m_pbState[m_i]; // Swap entries
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m_pbState[m_i] = m_pbState[m_j];
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m_pbState[m_j] = t;
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t = (byte)(m_pbState[m_i] + m_pbState[m_j]);
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pbRet[w] = m_pbState[t];
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}
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}
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}
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else { Debug.Assert(false); }
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return pbRet;
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}
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public ulong GetRandomUInt64()
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{
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byte[] pb = GetRandomBytes(8);
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return MemUtil.BytesToUInt64(pb);
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}
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#if CRSBENCHMARK
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public static string Benchmark()
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{
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int nRounds = 2000000;
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string str = "ArcFour small: " + BenchTime(CrsAlgorithm.ArcFourVariant,
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nRounds, 16).ToString() + "\r\n";
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str += "ArcFour big: " + BenchTime(CrsAlgorithm.ArcFourVariant,
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32, 2 * 1024 * 1024).ToString() + "\r\n";
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str += "Salsa20 small: " + BenchTime(CrsAlgorithm.Salsa20,
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nRounds, 16).ToString() + "\r\n";
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str += "Salsa20 big: " + BenchTime(CrsAlgorithm.Salsa20,
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32, 2 * 1024 * 1024).ToString();
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return str;
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}
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private static int BenchTime(CrsAlgorithm cra, int nRounds, int nDataSize)
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{
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byte[] pbKey = new byte[4] { 0x00, 0x01, 0x02, 0x03 };
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int nStart = Environment.TickCount;
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for(int i = 0; i < nRounds; ++i)
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{
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CryptoRandomStream c = new CryptoRandomStream(cra, pbKey);
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c.GetRandomBytes((uint)nDataSize);
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}
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int nEnd = Environment.TickCount;
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return (nEnd - nStart);
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}
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#endif
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}
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}
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