密碼加密器

//Description: Encrypting data from one stream to another and attaching hash of the password
using System.Security.Cryptography;
using System.IO;
using System.Data;
using System;
using System.Collections;
using System.ComponentModel;

public class PasswordEncryptor
{
 private byte[] _keyBytes;
 private byte[] _IVBytes;
 private int _bufferSize=256;
 private byte[] _hash;

 public PasswordEncryptor(string password)
 {
  byte[] saltValueBytes  = null;
  PasswordDeriveBytes pdb = new PasswordDeriveBytes(password,saltValueBytes,"SHA1",50);
  _keyBytes = pdb.GetBytes(32);
  _IVBytes = pdb.GetBytes(16);

  HashAlgorithm hasher = SHA256.Create();
  _hash = hasher.ComputeHash(System.Text.ASCIIEncoding.ASCII.GetBytes("password"));
 }

 public void EncryptWithHash(Stream input, ref Stream output)
 {
  output.Write(_hash,0,_hash.Length);

  RijndaelManaged rj = new System.Security.Cryptography.RijndaelManaged();
  rj.Mode= CipherMode.CBC;

  ICryptoTransform trans = rj.CreateEncryptor(_keyBytes, _IVBytes);

  CryptoStream cs = new CryptoStream(output, trans, CryptoStreamMode.Write);

  byte[] bytes = new byte[_bufferSize];

  int byteCount;

  while((byteCount = input.Read(bytes, 0, bytes.Length))!= 0)
  {
   cs.Write(bytes,0,byteCount);
  }

  cs.FlushFinalBlock();
  //cs.Close();
 }

 public void DecryptWithHash(Stream input, ref Stream output)
 {
  byte[] inputHash = new byte[_hash.Length];
  input.Read(inputHash,0,_hash.Length);

  if (inputHash.Length!=_hash.Length) throw new Exception("Invalid Password");

  for (int i=0;i<_hash.Length;i++)
  {
   if (_hash[i]!=inputHash[i]) throw new Exception("Invalid Password");
  }

  RijndaelManaged rj = new System.Security.Cryptography.RijndaelManaged();
  rj.Mode= CipherMode.CBC;

  ICryptoTransform trans = rj.CreateDecryptor(_keyBytes, _IVBytes);

  CryptoStream cs = new CryptoStream(input, trans, CryptoStreamMode.Read);

  byte[] bytes = new byte[_bufferSize];

  int byteCount;

  while((byteCount = cs.Read(bytes, 0, bytes.Length))!= 0)
  {
   output.Write(bytes,0,byteCount);
  }

  cs.Flush();
 }

}