C#加密解密文件

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

namespace ConsoleApplication
{
    public class EncryptKit
    {
        /// <summary>
        /// Call this function to remove the key from memory after use for security
        /// </summary>
        /// <param name="Destination"></param>
        /// <param name="Length"></param>
        /// <returns></returns>
        [System.Runtime.InteropServices.DllImport("KERNEL32.DLL", EntryPoint = "RtlZeroMemory")]
        public static extern bool ZeroMemory(IntPtr Destination, int Length);
        /// <summary>
        /// Function to Generate a 64 bits Key.
        /// </summary>
        /// <returns>返回生成的密钥</returns>
        public static string GenerateKey()
        {
            // Create an instance of Symetric Algorithm. Key and IV is generated automatically.
            DESCryptoServiceProvider desCrypto = (DESCryptoServiceProvider)DESCryptoServiceProvider.Create();
            // Use the Automatically generated key for Encryption.
            return ASCIIEncoding.ASCII.GetString(desCrypto.Key);
        }
        /// <summary>
        /// 加密文件
        /// </summary>
        /// <param name="sInputFilename">要加密的文件</param>
        /// <param name="sOutputFilename">加密后保存的文件</param>
        /// <param name="sKey">密钥</param>
        public static void EncryptFile(string sInputFilename, string sOutputFilename, string sKey)
        {
            using (FileStream fsInput = new FileStream(sInputFilename, FileMode.Open, FileAccess.Read))
            {
                byte[] bytearrayinput = new byte[fsInput.Length];
                fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
                fsInput.Close();

                FileStream fsEncrypted = new FileStream(sOutputFilename,
                   FileMode.OpenOrCreate,
                   FileAccess.Write);
                DESCryptoServiceProvider DES = new DESCryptoServiceProvider();

                DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
                DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);

                ICryptoTransform desencrypt = DES.CreateEncryptor();
                CryptoStream cryptostream = new CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write);
                cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
                cryptostream.Close();
                fsEncrypted.Close();
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sInputFilename">要解密的文件</param>
        /// <param name="sOutputFilename">解决后保存的文件</param>
        /// <param name="sKey">密钥</param>
        public static void DecryptFile(string sInputFilename, string sOutputFilename, string sKey)
        {
            DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
            //A 64 bit key and IV is required for this provider.
            //Set secret key For DES algorithm.
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            //Set initialization vector.
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);

            //Create a file stream to read the encrypted file back.
            using (FileStream fsread = new FileStream(sInputFilename, FileMode.Open, FileAccess.Read))
            {
                //Create a DES decryptor from the DES instance.
                ICryptoTransform desdecrypt = DES.CreateDecryptor();
                //Create crypto stream set to read and do a
                //DES decryption transform on incoming bytes.
                CryptoStream cryptostreamDecr = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read);
                //Print the contents of the decrypted file.
                StreamWriter fsDecrypted = new StreamWriter(sOutputFilename);
                fsDecrypted.Write(new StreamReader(cryptostreamDecr).ReadToEnd());
                fsDecrypted.Flush();
                fsDecrypted.Close();
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sInputFilename">要解密的文件路径</param>
        /// <param name="sKey">密钥</param>
        /// <returns>返回内容</returns>
        public static string DecryptFile(string sInputFilename, string sKey)
        {
            DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
            //A 64 bit key and IV is required for this provider.
            //Set secret key For DES algorithm.
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            //Set initialization vector.
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);

            //Create a file stream to read the encrypted file back.
            using (FileStream fsread = new FileStream(sInputFilename, FileMode.Open, FileAccess.Read))
            {
                byte[] byt = new byte[fsread.Length];
                fsread.Read(byt, 0, byt.Length);
                fsread.Flush();
                fsread.Close();
                //Create a DES decryptor from the DES instance.
                ICryptoTransform desdecrypt = DES.CreateDecryptor();
                MemoryStream ms = new MemoryStream();
                CryptoStream cryptostreamDecr = new CryptoStream(ms, desdecrypt, CryptoStreamMode.Write);
                cryptostreamDecr.Write(byt, 0, byt.Length);
                cryptostreamDecr.FlushFinalBlock();
                cryptostreamDecr.Close();
                return Encoding.UTF8.GetString(ms.ToArray()).Trim();
            }
        }
    }
}

  调用如下

  static void Main(string[] args)
        {
              sSecretKey = EncryptKit.GenerateKey();
            GCHandle gch = GCHandle.Alloc(sSecretKey, GCHandleType.Pinned);

            EncryptKit.EncryptFile(@"config.dat", @"config.dat", sSecretKey);
            EncryptKit.DecryptFile(@"config.dat", @"Decrypted.dat", sSecretKey);
            string str = EncryptKit.DecryptFile("config.dat", sSecretKey);
            Console.WriteLine(sSecretKey);
            EncryptKit.ZeroMemory(gch.AddrOfPinnedObject(), sSecretKey.Length * 2);
            gch.Free();
            Console.ReadKey();
        }