.NET下对二进制文件进行加密解密（C#）

下面的类实现了文件的加密和解密操作，试验了几种文件类型均没有问题，现在和大家共享一下。

namespace MyCryptoHelp
{
/// <summary>
/// 异常处理类
/// </summary>
public class CryptoHelpException : ApplicationException
{
   public CryptoHelpException(string msg):base(msg){}
}

/// <summary>
/// CryptHelp
/// </summary>
public class CryptoHelp
{
   private const ulong FC_TAG = 0xFC010203040506CF;

   private const int BUFFER_SIZE = 128*1024;
  
   /// <summary>
   /// 检验两个Byte数组是否相同
   /// </summary>
   /// <param name="b1">Byte数组</param>
   /// <param name="b2">Byte数组</param>
   /// <returns>true－相等</returns>
   private static bool CheckByteArrays(byte[] b1, byte[] b2)
   {
    if(b1.Length == b2.Length)
    {
     for(int i = 0; i < b1.Length; ++i)
     {
      if(b1[i] != b2[i])
       return false;
     }
     return true;
    }
    return false;
   }

   /// <summary>
   /// 创建Rijndael SymmetricAlgorithm
   /// </summary>
   /// <param name="password">密码</param>
   /// <param name="salt"></param>
   /// <returns>加密对象</returns>
   private static SymmetricAlgorithm CreateRijndael(string password, byte[] salt)
   {
    PasswordDeriveBytes pdb = new PasswordDeriveBytes(password,salt,"SHA256",1000);
   
    SymmetricAlgorithm sma = Rijndael.Create();
    sma.KeySize = 256;
    sma.Key = pdb.GetBytes(32);
    sma.Padding = PaddingMode.PKCS7;
    return sma;
   }

   /// <summary>
   /// 加密文件随机数生成
   /// </summary>
   private static RandomNumberGenerator rand = new RNGCryptoServiceProvider();

   /// <summary>
   /// 生成指定长度的随机Byte数组
   /// </summary>
   /// <param name="count">Byte数组长度</param>
   /// <returns>随机Byte数组</returns>
   private static byte[] GenerateRandomBytes(int count)
   {
    byte[] bytes = new byte[count];
    rand.GetBytes(bytes);
    return bytes;
   }

   /// <summary>
   /// 加密文件
   /// </summary>
   /// <param name="inFile">待加密文件</param>
   /// <param name="outFile">加密后输入文件</param>
   /// <param name="password">加密密码</param>
   public static void EncryptFile(string inFile, string outFile, string password)
   {
    using(FileStream fin = File.OpenRead(inFile),
        fout = File.OpenWrite(outFile))
    {
     long lSize = fin.Length; // 输入文件长度
     int size = (int)lSize;
     byte[] bytes = new byte[BUFFER_SIZE]; // 缓存
     int read = -1; // 输入文件读取数量
     int value = 0;
    
     // 获取IV和salt
     byte[] IV = GenerateRandomBytes(16);
     byte[] salt = GenerateRandomBytes(16);
    
     // 创建加密对象
     SymmetricAlgorithm sma = CryptoHelp.CreateRijndael(password, salt);
     sma.IV = IV;   
    
     // 在输出文件开始部分写入IV和salt
     fout.Write(IV,0,IV.Length);
     fout.Write(salt,0,salt.Length);
    
     // 创建散列加密
     HashAlgorithm hasher = SHA256.Create();
     using(CryptoStream cout = new CryptoStream(fout,sma.CreateEncryptor(),CryptoStreamMode.Write),
         chash = new CryptoStream(Stream.Null,hasher,CryptoStreamMode.Write))
     {
      BinaryWriter bw = new BinaryWriter(cout);
      bw.Write(lSize);
     
      bw.Write(FC_TAG);

      // 读写字节块到加密流缓冲区
      while( (read = fin.Read(bytes,0,bytes.Length)) != 0 )
      {
       cout.Write(bytes,0,read);
       chash.Write(bytes,0,read);
       value += read;
      }
      // 关闭加密流
      chash.Flush();
      chash.Close();

      // 读取散列
      byte[] hash = hasher.Hash;
     
      // 输入文件写入散列
      cout.Write(hash,0,hash.Length);

      // 关闭文件流
      cout.Flush();
      cout.Close();
     }
    }
   }

   /// <summary>
   /// 解密文件
   /// </summary>
   /// <param name="inFile">待解密文件</param>
   /// <param name="outFile">解密后输出文件</param>
   /// <param name="password">解密密码</param>
   public static void DecryptFile(string inFile, string outFile, string password)
   {
    // 创建打开文件流
    using(FileStream fin = File.OpenRead(inFile),
        fout = File.OpenWrite(outFile))
    {
     int size = (int)fin.Length;
     byte[] bytes = new byte[BUFFER_SIZE];
     int read = -1;
     int value = 0;
     int outValue = 0;

     byte[] IV = new byte[16];
     fin.Read(IV,0,16);
     byte[] salt = new byte[16];
     fin.Read(salt,0,16);
    
     SymmetricAlgorithm sma = CryptoHelp.CreateRijndael(password,salt);
     sma.IV = IV;

     value = 32;
     long lSize = -1;
    
     // 创建散列对象, 校验文件
     HashAlgorithm hasher = SHA256.Create();

     using(CryptoStream cin = new CryptoStream(fin,sma.CreateDecryptor(),CryptoStreamMode.Read),
         chash = new CryptoStream(Stream.Null,hasher,CryptoStreamMode.Write))
     {
      // 读取文件长度
      BinaryReader br = new BinaryReader(cin);
      lSize = br.ReadInt64();
      ulong tag = br.ReadUInt64();
     
      if(FC_TAG != tag)
       throw new CryptoHelpException("文件被破坏");
     
      long numReads = lSize / BUFFER_SIZE;

      long slack = (long)lSize % BUFFER_SIZE;
     
      for(int i = 0; i < numReads; ++i)
      {
       read = cin.Read(bytes,0,bytes.Length);
       fout.Write(bytes,0,read);
       chash.Write(bytes,0,read);
       value += read;
       outValue += read;
      }

      if(slack > 0)
      {
       read = cin.Read(bytes,0,(int)slack);
       fout.Write(bytes,0,read);
       chash.Write(bytes,0,read);
       value += read;
       outValue += read;
      }

      chash.Flush();
      chash.Close();

      fout.Flush();
      fout.Close();

      byte[] curHash = hasher.Hash;

      // 获取比较和旧的散列对象
      byte[] oldHash = new byte[hasher.HashSize / 8];
      read = cin.Read(oldHash,0,oldHash.Length);
      if((oldHash.Length != read) || (!CheckByteArrays(oldHash,curHash)))
       throw new CryptoHelpException("文件被破坏");
     }
    
     if(outValue != lSize)
      throw new CryptoHelpException("文件大小不匹配");
    }
   }
}
}

// 调用

public class TestClass
{
     string myPassword = "TEST_PASSWORD_~!@#";
     string myPlainFile = "test.txt";
     string myEncryptedFile = "test.encrypted";
     string myDecryptedFile = "test.decrypted";

     [STAThread]
     static void Main()
     {
         CryptoHelp.EncryptFile(myPlainFile, myEncryptedFile, myPassword);
         CryptoHelp.DecryptFile(myEncryptedFile,myDecryptedFile, myPassword);
     }
}