public static class EncryptAndDecrypt
     {
         //加密
         public static string Encrypt(string input)
         {
             // 鹽值
             string saltValue = "saltValue";
             // 密碼值
             string pwdValue = "pwdValue";
             byte[] data = System.Text.UTF8Encoding.UTF8.GetBytes(input);
             byte[] salt = System.Text.UTF8Encoding.UTF8.GetBytes(saltValue);
             // AesManaged - 高級加密標準(AES) 對稱算法的管理類
             System.Security.Cryptography.AesManaged aes = new System.Security.Cryptography.AesManaged();
             // Rfc2898DeriveBytes - 通過使用基于 HMACSHA1 的偽隨機數生成器，實現基于密碼的密鑰派生功能 (PBKDF2 - 一種基于密碼的密鑰派生函數)
             // 通過 密碼 和 salt 派生密鑰
             System.Security.Cryptography.Rfc2898DeriveBytes rfc = new System.Security.Cryptography.Rfc2898DeriveBytes(pwdValue, salt);
             /**/
             /*
          * AesManaged.BlockSize - 加密操作的塊大小（單位：bit）
          * AesManaged.LegalBlockSizes - 對稱算法支持的塊大小（單位：bit）
          * AesManaged.KeySize - 對稱算法的密鑰大小（單位：bit）
          * AesManaged.LegalKeySizes - 對稱算法支持的密鑰大小（單位：bit）
          * AesManaged.Key - 對稱算法的密鑰
          * AesManaged.IV - 對稱算法的密鑰大小
          * Rfc2898DeriveBytes.GetBytes(int 需要生成的偽隨機密鑰字節數) - 生成密鑰
          */
             aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;
             aes.KeySize = aes.LegalKeySizes[0].MaxSize;
             aes.Key = rfc.GetBytes(aes.KeySize / 8);
             aes.IV = rfc.GetBytes(aes.BlockSize / 8);
             // 用當前的 Key 屬性和初始化向量 IV 創建對稱加密器對象
             System.Security.Cryptography.ICryptoTransform encryptTransform = aes.CreateEncryptor();
             // 加密后的輸出流
             System.IO.MemoryStream encryptStream = new System.IO.MemoryStream();
             // 將加密后的目標流（encryptStream）與加密轉換（encryptTransform）相連接
             System.Security.Cryptography.CryptoStream encryptor = new System.Security.Cryptography.CryptoStream
                 (encryptStream, encryptTransform, System.Security.Cryptography.CryptoStreamMode.Write);
             // 將一個字節序列寫入當前 CryptoStream （完成加密的過程）
             encryptor.Write(data, 0, data.Length);
             encryptor.Close();
             // 將加密后所得到的流轉換成字節數組，再用Base64編碼將其轉換為字符串
             string encryptedString = Convert.ToBase64String(encryptStream.ToArray());
             return encryptedString;
         }

 
         #region silverlight密碼解密
         /**/
         /// <summary>
         /// 解密數據
         /// </summary>
         /// <param name="input">加密后的字符串</param>
         /// <returns>加密前的字符串</returns>
         public static string Decrypt(string input)
         {
             // 鹽值（與加密時設置的值一致）
             string saltValue = "saltValue";
             // 密碼值（與加密時設置的值一致）
             string pwdValue = "pwdValue";
             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[0].MaxSize;
             aes.KeySize = aes.LegalKeySizes[0].MaxSize;
             aes.Key = rfc.GetBytes(aes.KeySize / 8);
             aes.IV = rfc.GetBytes(aes.BlockSize / 8);
             // 用當前的 Key 屬性和初始化向量 IV 創建對稱解密器對象
             System.Security.Cryptography.ICryptoTransform decryptTransform = aes.CreateDecryptor();
             // 解密后的輸出流
             MemoryStream decryptStream = new MemoryStream();
             // 將解密后的目標流（decryptStream）與解密轉換（decryptTransform）相連接
             System.Security.Cryptography.CryptoStream decryptor = new System.Security.Cryptography.CryptoStream(
                 decryptStream, decryptTransform, System.Security.Cryptography.CryptoStreamMode.Write);
             // 將一個字節序列寫入當前 CryptoStream （完成解密的過程）
             decryptor.Write(encryptBytes, 0, encryptBytes.Length);
             decryptor.Close();
             // 將解密后所得到的流轉換為字符串
             byte[] decryptBytes = decryptStream.ToArray();
             string decryptedString = UTF8Encoding.UTF8.GetString(decryptBytes, 0, decryptBytes.Length);
             return decryptedString;
         }
         #endregion
     }