using System;

using OtpNet;

using System.Text;

public class Program

{

    private static string ParentGuid = "3564a05b-1d18-4754-9352-a803b1e20554";

    private static DateTime VerificationCodeCreated = DateTime.Now;

    private static int VerificationCodeExpirationInSeconds =  300;

    public static void Main()

    {

        var totpCode = GenerateTotpCode();

        Console.WriteLine($"{nameof(totpCode)}: {totpCode}");

        bool success = VerifyTotpCode(totpCode);

        Console.WriteLine($"{nameof(success)}: {success}");

    }

    private static string GenerateTotpCode()

    {

        var totp = GetTotpForParent();

        var totpCode = totp.ComputeTotp();

        Console.WriteLine(totp.RemainingSeconds());

​

        return totpCode;        

    }

    private static bool VerifyTotpCode(string totpCode)

    {

        var totp = GetTotpForParent();

        long timeWindowUsed;        

        bool success = totp.VerifyTotp(totpCode, out timeWindowUsed, new VerificationWindow(previous:1));

        return success;

    }

    private static Totp GetTotpForParent()

    {

        var secretKey = Encoding.UTF8.GetBytes(ParentGuid);     

        var totp = new Totp(secretKey, mode: OtpHashMode.Sha512, step: VerificationCodeExpirationInSeconds);

        return totp;

    }

}