using System;

using System.Text;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(new HMACSHA1(

            Encoding.UTF8.GetBytes("4752f32b-ac5a-46cd-9061-fb6a856ac925")

        ).ComputeHash(

            Encoding.UTF8.GetBytes(@"{""alerts"": [], ""external_id"": ""9bc9e473-6b4e-422e-89cd-56ba93e5f3ff""}")

        ).ToString());

    }

}

​