using System;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    public static void Main()

    {

        var keyId = "8d6d26a3-2f81-459e-b668-64a922eba891";

        var secret = "QDZpf2GHreX9f71ZIUEy";

        const string tokenType = "AccessKey";

        var timestamp = DateTimeOffset.UtcNow.ToUnixTimeSeconds();

​

        var payload = $"{tokenType} {keyId} {timestamp}";

        var secretBytes = Encoding.UTF8.GetBytes(secret);

        using var hmac = new HMACSHA256(secretBytes);

        var hashBytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(payload));

        var signature = Base64Encode(ToHexString(hashBytes));

        var authorizationHeader = $"{tokenType} {keyId} {timestamp} {signature}";

        Console.WriteLine(authorizationHeader);

    }

    public static string ToHexString(byte[] array)

    {

        StringBuilder hex = new StringBuilder(array.Length * 2);

        foreach (byte b in array)

        {

            hex.AppendFormat("{0:x2}", b);

        }

        return hex.ToString();

    }

    public static string Base64Encode(string plainText) 

    {

      var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);

      return System.Convert.ToBase64String(plainTextBytes);

    }

}

​