C# 加密和解密文件

相关示例代码如下：
  1 using System;
  2 using System.IO;
  3 using System.Security;
  4 using System.Security.Cryptography;
  5 using System.Runtime.InteropServices;
  6 using System.Text;
  7 
  8 namespace CSEncryptDecrypt
  9 {
 10    class Class1
 11    {
 12       //  Call this function to remove the key from memory after use for security
 13       [System.Runtime.InteropServices.DllImport("KERNEL32.DLL", EntryPoint="RtlZeroMemory")]
 14       public static extern bool ZeroMemory(IntPtr Destination, int Length);
 15         
 16       // Function to Generate a 64 bits Key.
 17       static string GenerateKey() 
 18       {
 19          // Create an instance of Symetric Algorithm. Key and IV is generated automatically.
 20          DESCryptoServiceProvider desCrypto =(DESCryptoServiceProvider)DESCryptoServiceProvider.Create();
 21 
 22          // Use the Automatically generated key for Encryption. 
 23          return ASCIIEncoding.ASCII.GetString(desCrypto.Key);
 24       }
 25 
 26       static void EncryptFile(string sInputFilename,
 27          string sOutputFilename, 
 28          string sKey) 
 29       {
 30          FileStream fsInput = new FileStream(sInputFilename, 
 31             FileMode.Open, 
 32             FileAccess.Read);
 33 
 34          FileStream fsEncrypted = new FileStream(sOutputFilename, 
 35             FileMode.Create, 
 36             FileAccess.Write);
 37          DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
 38          DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
 39          DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
 40          ICryptoTransform desencrypt = DES.CreateEncryptor();
 41          CryptoStream cryptostream = new CryptoStream(fsEncrypted, 
 42             desencrypt, 
 43             CryptoStreamMode.Write); 
 44 
 45          byte[] bytearrayinput = new byte[fsInput.Length];
 46          fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
 47          cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
 48          cryptostream.Close();
 49          fsInput.Close();
 50          fsEncrypted.Close();
 51       }
 52 
 53       static void DecryptFile(string sInputFilename, 
 54          string sOutputFilename,
 55          string sKey)
 56       {
 57          DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
 58          //A 64 bit key and IV is required for this provider.
 59          //Set secret key For DES algorithm.
 60          DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
 61          //Set initialization vector.
 62          DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
 63 
 64          //Create a file stream to read the encrypted file back.
 65          FileStream fsread = new FileStream(sInputFilename, 
 66             FileMode.Open, 
 67             FileAccess.Read);
 68          //Create a DES decryptor from the DES instance.
 69          ICryptoTransform desdecrypt = DES.CreateDecryptor();
 70          //Create crypto stream set to read and do a 
 71          //DES decryption transform on incoming bytes.
 72          CryptoStream cryptostreamDecr = new CryptoStream(fsread, 
 73             desdecrypt,
 74             CryptoStreamMode.Read);
 75          //Print the contents of the decrypted file.
 76          StreamWriter fsDecrypted = new StreamWriter(sOutputFilename);
 77          fsDecrypted.Write(new StreamReader(cryptostreamDecr).ReadToEnd());
 78          fsDecrypted.Flush();
 79          fsDecrypted.Close();
 80       } 
 81 
 82       static void Main()
 83       {
 84          // Must be 64 bits, 8 bytes.
 85          // Distribute this key to the user who will decrypt this file.
 86          string sSecretKey;
 87          
 88          // Get the Key for the file to Encrypt.
 89          sSecretKey = GenerateKey();
 90 
 91          // For additional security Pin the key.
 92          GCHandle gch = GCHandle.Alloc( sSecretKey,GCHandleType.Pinned );
 93          
 94          // Encrypt the file.        
 95          EncryptFile(@"C:MyData.txt", 
 96             @"C:Encrypted.txt", 
 97             sSecretKey);
 98 
 99          // Decrypt the file.
100          DecryptFile(@"C:Encrypted.txt", 
101             @"C:Decrypted.txt", 
102             sSecretKey);
103 
104          // Remove the Key from memory. 
105          ZeroMemory(gch.AddrOfPinnedObject(), sSecretKey.Length * 2);
106          gch.Free();
107       }
108    }
109 }