https://stackoverflow.com/a/44116352

public class DigestAuthenticationFilterAttribute : ActionFilterAttribute
{
    private const string AUTH_HEADER_NAME = "Authorization";
    private const string AUTH_METHOD_NAME = "Digest ";
    private AuthenticationSettings _settings;

    public DigestAuthenticationFilterAttribute(IOptions<AuthenticationSettings> settings)
    {
        _settings = settings.Value;
    }

    public override void OnActionExecuting(ActionExecutingContext context)
    {
        ValidateSecureChannel(context?.HttpContext?.Request);
        ValidateAuthenticationHeaders(context?.HttpContext?.Request);
        base.OnActionExecuting(context);
    }

    private void ValidateSecureChannel(HttpRequest request)
    {
        if (_settings.RequireSSL && !request.IsHttps)
        {
            throw new AuthenticationException("This service must be called using HTTPS");
        }
    }

    private void ValidateAuthenticationHeaders(HttpRequest request)
    {
        string authHeader = GetRequestAuthorizationHeaderValue(request);
        string digest = (authHeader != null && authHeader.StartsWith(AUTH_METHOD_NAME)) ? authHeader.Substring(AUTH_METHOD_NAME.Length) : null;
        if (string.IsNullOrEmpty(digest))
        {
            throw new AuthenticationException("You must send your credentials using Authorization header");
        }
        if (digest != CalculateSHA1($"{_settings.UserName}:{_settings.Password}"))
        {
            throw new AuthenticationException("Invalid credentials");
        }

    }

    private string GetRequestAuthorizationHeaderValue(HttpRequest request)
    {
        return request.Headers.Keys.Contains(AUTH_HEADER_NAME) ? request.Headers[AUTH_HEADER_NAME].First() : null;
    }

    public static string CalculateSHA1(string text)
    {
        var sha1 = System.Security.Cryptography.SHA1.Create();
        var hash = sha1.ComputeHash(Encoding.UTF8.GetBytes(text));
        return Convert.ToBase64String(hash);
    }
}