jwt authentication filter c#

using System;
using System.Security.Principal;
using System.Threading;
using System.Threading.Tasks;
using System.Web.Http.Filters;
namespace myspace.filters
{
    public class JwtAuthenticationAttribute : Attribute, IAuthenticationFilter
    {
        private ILog log = LogFactory.GetLogger("JwtAuthValidationLogs");


        public string Realm { get; set; }
        public bool AllowMultiple => false;

        public async Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
        {
            log.Info("Authenticating JWT");
            
            var request = context.Request;
            var authorization = request.Headers.Authorization;

            if (authorization == null || authorization.Scheme != "Bearer")
            {
                context.ErrorResult = new AuthenticationFailureResult("Missing Jwt Token", request);
                return;
            }

            if (string.IsNullOrEmpty(authorization.Parameter))
            {
                context.ErrorResult = new AuthenticationFailureResult("Missing Jwt Token", request);
                return;
            }

            var token = authorization.Parameter;
            try
            {
                IPrincipal principal = await SecurityUtils.validateToken(token);

                if (principal == null)
                {
                    context.ErrorResult = new AuthenticationFailureResult("Invalid token", request);

                }
                else
                {
                    context.Principal = principal;
                }

            }
            catch (Exception ex)
            {
                log.Error("Exception occured Validating Jwt Token "+ ex.Message + " Inner Exception : " + ex.InnerException);
                context.ErrorResult = new AuthenticationFailureResult("Invalid token", request);
            }
        }
        public Task ChallengeAsync(HttpAuthenticationChallengeContext context, CancellationToken cancellationToken)
        {

            return Task.FromResult(0);
        }




    }
}