Codeclass DES    {        /// 
        /// Call this function to remove the key from memory after use for security        /// 
        ///         ///         /// 
             [System.Runtime.InteropServices.DllImport("KERNEL32.DLL", EntryPoint = "RtlZeroMemory")]        public static extern bool ZeroMemory(IntPtr Destination, int Length);        /// 
        /// Function to Generate a 64 bits Key.        /// 
        /// 
     
      返回生成的密钥
             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);        }        #region 加密文件        /// 
        /// 加密文件        /// 
        /// 要加密的文件        /// 加密后保存的文件        /// 密钥        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();            }        }        #endregion        #region 解密文件        /// 
        /// 解密文件        /// 
        /// 要解密的文件        /// 解决后保存的文件        /// 密钥        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();            }        }        /// 
        /// 解密文件并返回内容        /// 
        /// 要解密的文件路径        /// 密钥        /// 
     
      返回内容
             public static string DecryptFile(string sInputFilename, string sKey)        {            try            {                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();                }            }            catch            {                return "";            }        }        #endregion        #region DES加密        /// 
        /// DES加密        /// 
        /// 需要加密的字符串        /// 
     
      加密后的字符串
             public static string DESEncrypt(string pToEncrypt, string DesKeyStr)        {            try            {                DESCryptoServiceProvider des = new DESCryptoServiceProvider();                byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);                des.Key = ASCIIEncoding.ASCII.GetBytes(DesKeyStr);                des.IV = ASCIIEncoding.ASCII.GetBytes(DesKeyStr);                MemoryStream ms = new MemoryStream();                CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);                cs.Write(inputByteArray, 0, inputByteArray.Length);                cs.FlushFinalBlock();                StringBuilder ret = new StringBuilder();                foreach (byte b in ms.ToArray())                {                    ret.AppendFormat("{0:X2}", b);                }                ret.ToString();                return ret.ToString();            }            catch            {                System.Windows.Forms.MessageBox.Show("输入注册码错误，请重新输入！！");                return "";            }        }        #endregion        #region DES解密        /// 
        /// DES解密        /// 
        /// 加密后的字符串        /// 
     
      解密后的字符串
             public static string DESDecrypt(string pToDecrypt, string DesKeyStr)        {            try            {                DESCryptoServiceProvider des = new DESCryptoServiceProvider();                byte[] inputByteArray = new byte[pToDecrypt.Length / 2];                for (int x = 0; x < pToDecrypt.Length / 2; x++)                {                    int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));                    inputByteArray[x] = (byte)i;                }                des.Key = ASCIIEncoding.ASCII.GetBytes(DesKeyStr);                des.IV = ASCIIEncoding.ASCII.GetBytes(DesKeyStr);                MemoryStream ms = new MemoryStream();                CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);                cs.Write(inputByteArray, 0, inputByteArray.Length);                cs.FlushFinalBlock();                StringBuilder ret = new StringBuilder();                return System.Text.Encoding.Default.GetString(ms.ToArray());            }            catch            {                System.Windows.Forms.MessageBox.Show("输入注册码错误，请重新输入！！");                return "";            }        }        #endregion    }