using System;

using System.Collections.Generic;

using System.Security.Cryptography;

using Jose;

public class Program

{

    public static void Main()

    {

        var iat = Math.Round((DateTime.UtcNow.AddMinutes(-1) - new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds, 0);

        var exp = Math.Round((DateTime.UtcNow.AddMinutes(30) - new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds, 0);

        var payload = new Dictionary<string, object>()

        {

            { "iat", iat },

            { "exp", exp },

            { "iss", "My team ID" },

            { "origin", "My domain name" }

        };

        var extraHeader = new Dictionary<string, object>()

        {

            { "alg", "ES256" },

            { "typ", "JWT" },

            { "kid", "My key ID" }

        };

        var keyString = "the content of my .p8 downloaded private key, when I created the key in https://developer.apple.com/account/ios/authkey/create";

        CngKey privateKey = CngKey.Import(Convert.FromBase64String(keyString), CngKeyBlobFormat.Pkcs8PrivateBlob);

        string token = JWT.Encode(payload, privateKey, JwsAlgorithm.ES256, extraHeader);

        Console.WriteLine(token);

    }

}