Crypto number

    class App
    {
        static void Main(string[] argv)
        {
            int len = 12;
            if (argv.Length > 0)
                len = int.Parse(argv[0]);
            byte[] buff = new byte[len / 2];
            RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
            rng.GetBytes(buff);
            StringBuilder sb = new StringBuilder(len);
            for (int i = 0; i < buff.Length; i++)
                sb.Append(string.Format("{0:X2}", buff[i]));
            Console.WriteLine(sb);
        }
    }