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using system;

using system.IO;

using system.Text;

using system.Security.Cryptography;

 

 

namespace Rextester

    public class Program

    {

        public static void Main(string[] args)

        {          

            Console.WriteLine(Decrypt("mfyJCIiTg8CiPTU38g88EQ=="));

        }

        public static string Decrypt(string cipherText)

        {

            string EncryptionKey = "MAKV2SPBNI99212";

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

            using (Aes encryptor = Aes.Create())

            {

                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

                encryptor.Key = pdb.GetBytes(32);

                encryptor.IV = pdb.GetBytes(16);

                using (MemoryStream ms = new MemoryStream())

                {

                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))

                    {

                        cs.Write(cipherBytes, 0, cipherBytes.Length);

                        cs.Close();

                    }

                    cipherText = Encoding.Unicode.GetString(ms.ToArray());

                }

            }

            return cipherText;

        }

    }