using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    public static void Main()

    {

         string encryptionKey = "KRHE7HGVNE32653";

        string clearText="987";

            byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);

            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.CreateEncryptor(), CryptoStreamMode.Write))

                    {

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

                        cs.Close();

                    }

                    clearText = Convert.ToBase64String(ms.ToArray());

                }

            }

           Console.WriteLine(clearText);

        }

    }

​