Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Security / Cryptography / Rfc2898DeriveBytes.cs / 1 / Rfc2898DeriveBytes.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // // Rfc2898DeriveBytes.cs // // This implementation follows RFC 2898 recommendations. See http://www.ietf.org/rfc/Rfc2898.txt // It uses HMACSHA1 as the underlying pseudorandom function. namespace System.Security.Cryptography { using System.Globalization; using System.IO; using System.Text; [System.Runtime.InteropServices.ComVisible(true)] public class Rfc2898DeriveBytes : DeriveBytes { private byte[] m_buffer; private byte[] m_salt; private HMACSHA1 m_hmacsha1; // The pseudo-random generator function used in PBKDF2 private uint m_iterations; private uint m_block; private int m_startIndex; private int m_endIndex; private const int BlockSize = 20; // // public constructors // public Rfc2898DeriveBytes(string password, int saltSize) : this(password, saltSize, 1000) {} public Rfc2898DeriveBytes(string password, int saltSize, int iterations) { if (saltSize < 0) throw new ArgumentOutOfRangeException("saltSize", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); byte[] salt = new byte[saltSize]; Utils.StaticRandomNumberGenerator.GetBytes(salt); Salt = salt; IterationCount = iterations; m_hmacsha1 = new HMACSHA1(new UTF8Encoding(false).GetBytes(password)); Initialize(); } public Rfc2898DeriveBytes(string password, byte[] salt) : this(password, salt, 1000) {} public Rfc2898DeriveBytes(string password, byte[] salt, int iterations) : this (new UTF8Encoding(false).GetBytes(password), salt, iterations) {} public Rfc2898DeriveBytes(byte[] password, byte[] salt, int iterations) { Salt = salt; IterationCount = iterations; m_hmacsha1 = new HMACSHA1(password); Initialize(); } // // public properties // public int IterationCount { get { return (int) m_iterations; } set { if (value <= 0) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); m_iterations = (uint) value; Initialize(); } } public byte[] Salt { get { return (byte[]) m_salt.Clone(); } set { if (value == null) throw new ArgumentNullException("value"); if (value.Length < 8) throw new ArgumentException(String.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("Cryptography_PasswordDerivedBytes_FewBytesSalt"))); m_salt = (byte[]) value.Clone(); Initialize(); } } // // public methods // public override byte[] GetBytes(int cb) { if (cb <= 0) throw new ArgumentOutOfRangeException("cb", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); byte[] password = new byte[cb]; int offset = 0; int size = m_endIndex - m_startIndex; if (size > 0) { if (cb >= size) { Buffer.InternalBlockCopy(m_buffer, m_startIndex, password, 0, size); m_startIndex = m_endIndex = 0; offset += size; } else { Buffer.InternalBlockCopy(m_buffer, m_startIndex, password, 0, cb); m_startIndex += cb; return password; } } BCLDebug.Assert(m_startIndex == 0 && m_endIndex == 0, "Invalid start or end index in the internal buffer." ); while(offset < cb) { byte[] T_block = Func(); int remainder = cb - offset; if(remainder > BlockSize) { Buffer.InternalBlockCopy(T_block, 0, password, offset, BlockSize); offset += BlockSize; } else { Buffer.InternalBlockCopy(T_block, 0, password, offset, remainder); offset += remainder; Buffer.InternalBlockCopy(T_block, remainder, m_buffer, m_startIndex, BlockSize - remainder); m_endIndex += (BlockSize - remainder); return password; } } return password; } public override void Reset() { Initialize(); } private void Initialize() { if (m_buffer != null) Array.Clear(m_buffer, 0, m_buffer.Length); m_buffer = new byte[BlockSize]; m_block = 1; m_startIndex = m_endIndex = 0; } // This function is defined as follow : // Func (S, i) = HMAC(S || i) | HMAC2(S || i) | ... | HMAC(iterations) (S || i) // where i is the block number. private byte[] Func () { byte[] INT_block = Utils.Int(m_block); m_hmacsha1.TransformBlock(m_salt, 0, m_salt.Length, m_salt, 0); m_hmacsha1.TransformFinalBlock(INT_block, 0, INT_block.Length); byte[] temp = m_hmacsha1.Hash; m_hmacsha1.Initialize(); byte[] ret = temp; for (int i = 2; i <= m_iterations; i++) { temp = m_hmacsha1.ComputeHash(temp); for (int j = 0; j < BlockSize; j++) { ret[j] ^= temp[j]; } } // increment the block count. m_block++; return ret; } } }
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