using System;

using System.Security.Cryptography;

using System.Text;

using System.Linq;

public class Program

{

    public static byte[] GetKey(string siteSecret)

    {

        byte[] key = Encoding.UTF8.GetBytes(siteSecret);

        return SHA1.Create().ComputeHash(key).Take(16).ToArray();

    }

​

    public static string EncryptAes(string input, string siteSecret)

    {

        var key = GetKey(siteSecret);

        using (var aes = AesManaged.Create())

        {

            if (aes == null) return null;

​

            aes.Mode = CipherMode.ECB;

            aes.Padding = PaddingMode.PKCS7;

            aes.Key = key;

            byte[] inputBytes = Encoding.UTF8.GetBytes(input);

​

            var enc = aes.CreateEncryptor(key, new byte[16]);

            return UrlSafeBase64(enc.TransformFinalBlock(inputBytes,0,input.Length));

        }

    }

​

    // http://stackoverflow.com/a/26354677/162671

    public static string UrlSafeBase64(byte[] bytes)

    {

        return Convert.ToBase64String(bytes).TrimEnd('=')

            .Replace('+', '-')

            .Replace('/', '_');

    }

    public static void Main(string[] args)

    {

        string siteSecret = "12345678";

        string jsonToken = "{'session_id':'abf52ca5-9d87-4061-b109-334abb7e637a','ts_ms':1445705791480}";

​

        Console.WriteLine(" json token: " + jsonToken);

        Console.WriteLine(" siteSecret: " + siteSecret);

        Console.WriteLine(EncryptAes(jsonToken, siteSecret));

        Console.ReadLine();

    }

}