public class EncryptHepler {

         // 验值

         static string saltValue = "XXXX";

         // 密码值

         static string pwdValue = "XXXX";

         /// <summary>

         /// 加密

         /// </summary>

         public static string Encrypt( string input ) {

             byte[ ] data = System.Text.UTF8Encoding.UTF8.GetBytes( input );

             byte[ ] salt = System.Text.UTF8Encoding.UTF8.GetBytes( saltValue );

             // AesManaged - 高级加密标准(AES) 对称算法的管理类

             System.Security.Cryptography.AesManaged aes = new System.Security.Cryptography.AesManaged( );

             // Rfc2898DeriveBytes - 通过使用基于 HMACSHA1 的伪随机数生成器，实现基于密码的密钥派生功能 (PBKDF2 - 一种基于密码的密钥派生函数)

             // 通过 密码 和 salt 派生密钥

             System.Security.Cryptography.Rfc2898DeriveBytes rfc = new System.Security.Cryptography.Rfc2898DeriveBytes( pwdValue, salt );

             aes.BlockSize = aes.LegalBlockSizes[].MaxSize;

             aes.KeySize = aes.LegalKeySizes[].MaxSize;

             aes.Key = rfc.GetBytes( aes.KeySize /  );

             aes.IV = rfc.GetBytes( aes.BlockSize /  );

             // 用当前的 Key 属性和初始化向量 IV 创建对称加密器对象

             System.Security.Cryptography.ICryptoTransform encryptTransform = aes.CreateEncryptor( );

             // 加密后的输出流

             System.IO.MemoryStream encryptStream = new System.IO.MemoryStream( );

             // 将加密后的目标流（encryptStream）与加密转换（encryptTransform）相连接

             System.Security.Cryptography.CryptoStream encryptor = new System.Security.Cryptography.CryptoStream

                 ( encryptStream, encryptTransform, System.Security.Cryptography.CryptoStreamMode.Write );

             // 将一个字节序列写入当前 CryptoStream （完成加密的过程）

             encryptor.Write( data, , data.Length );

             encryptor.Close( );

             // 将加密后所得到的流转换成字节数组，再用Base64编码将其转换为字符串

             string encryptedString = Convert.ToBase64String( encryptStream.ToArray( ) );

             return encryptedString;

         }

 /// <summary>

         /// 解密

         /// </summary>

         public static string Decrypt( string input ) {

             byte[ ] encryptBytes = Convert.FromBase64String( input );

             byte[ ] salt = Encoding.UTF8.GetBytes( saltValue );

             System.Security.Cryptography.AesManaged aes = new System.Security.Cryptography.AesManaged( );

             System.Security.Cryptography.Rfc2898DeriveBytes rfc = new System.Security.Cryptography.Rfc2898DeriveBytes( pwdValue, salt );

             aes.BlockSize = aes.LegalBlockSizes[].MaxSize;

             aes.KeySize = aes.LegalKeySizes[].MaxSize;

             aes.Key = rfc.GetBytes( aes.KeySize /  );

             aes.IV = rfc.GetBytes( aes.BlockSize /  );

             // 用当前的 Key 属性和初始化向量 IV 创建对称解密器对象

             System.Security.Cryptography.ICryptoTransform decryptTransform = aes.CreateDecryptor( );

             // 解密后的输出流

             System.IO.MemoryStream decryptStream = new System.IO.MemoryStream( );

             // 将解密后的目标流（decryptStream）与解密转换（decryptTransform）相连接

             System.Security.Cryptography.CryptoStream decryptor = new System.Security.Cryptography.CryptoStream(

                 decryptStream, decryptTransform, System.Security.Cryptography.CryptoStreamMode.Write );

             // 将一个字节序列写入当前 CryptoStream （完成解密的过程）

             decryptor.Write( encryptBytes, , encryptBytes.Length );

             decryptor.Close( );

             // 将解密后所得到的流转换为字符串

             byte[ ] decryptBytes = decryptStream.ToArray( );

             string decryptedString = UTF8Encoding.UTF8.GetString( decryptBytes, , decryptBytes.Length );

             return decryptedString;

         }

     }//class end