using System;

using System.Text;

using System.IO;

using System.Security.Cryptography;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Encrypt("130722"));

        Console.WriteLine(Decrypt("y0tfuMZUA/UEOf0pb8NlFg=="));

    }

​

    private const String SHARED_PASSPHASE = "S@rva!R3l0";

    // This constant string is used as a "salt" value for the PasswordDeriveBytes function calls.

    // This size of the IV (in bytes) must = (keysize / 8).  Default keysize is 256, so the IV must be

    // 32 bytes long.  Using a 16 character string here gives us 32 bytes when converted to a byte array.

    private static readonly byte[] initVectorBytes = Encoding.ASCII.GetBytes("4hkd852l08mslMrF");

    // This constant is used to determine the keysize of the encryption algorithm.

    private const int keysize = 256;

    public static string Encrypt(string plainText)

    {

        if (String.IsNullOrEmpty(plainText))

        {

            return plainText;

        }

​

        byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

        using (PasswordDeriveBytes password = new PasswordDeriveBytes(SHARED_PASSPHASE, null))

        {

            byte[] keyBytes = password.GetBytes(keysize / 8);

            using (RijndaelManaged symmetricKey = new RijndaelManaged())

            {

                symmetricKey.Mode = CipherMode.CBC;

                using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes))

                {

                    using (MemoryStream memoryStream = new MemoryStream())

                    {

                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))

                        {

                            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);

                            cryptoStream.FlushFinalBlock();

                            byte[] cipherTextBytes = memoryStream.ToArray();

                            return Convert.ToBase64String(cipherTextBytes);

                        }

                    }

                }

            }

        }

    }

​

    public static string Decrypt(string cipherText)

    {

        if (String.IsNullOrEmpty(cipherText))

        {

            return cipherText;

        }

​

        byte[] cipherTextBytes = Convert.FromBase64String(cipherText);

        using (PasswordDeriveBytes password = new PasswordDeriveBytes(SHARED_PASSPHASE, null))

        {

            byte[] keyBytes = password.GetBytes(keysize / 8);

            using (RijndaelManaged symmetricKey = new RijndaelManaged())

            {

                symmetricKey.Mode = CipherMode.CBC;

                using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes))

                {

                    using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))

                    {

                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))

                        {

                            byte[] plainTextBytes = new byte[cipherTextBytes.Length];

                            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);

                            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);

                        }

                    }

                }

            }

        }

    }

}