如何使用签名保证ASP.NET MVC OR WEBAPI的接口安全

 public static string HmacSHA256(string secretKey,string plain)
        {
            var keyBytes = Encoding.UTF8.GetBytes(secretKey);
            var plainBytes = Encoding.UTF8.GetBytes(plain);

            using (var hmacsha256 = new HMACSHA256(keyBytes))
            {
                var sb = new StringBuilder();
                var hashValue = hmacsha256.ComputeHash(plainBytes);
                foreach (byte x in hashValue)
                {
                    sb.Append(String.Format("{0:x2}", x));
                }
                return sb.ToString();
            }
        }

 public static string MakeSignPlain(SortedDictionary<string,string> queryString,string time,string random )
        {
            var sb = new StringBuilder();
            foreach (var keyValue in queryString)
            {
                sb.AppendFormat("{0}={1}&", keyValue.Key, keyValue.Value);
            }
            if (sb.Length>1)
            {
                sb.Remove(sb.Length - 1, 1);
            }
            sb.Append(time);
            sb.Append(random);

            return sb.ToString().ToUpper();
        }

 public static bool Valid(string requestSign,string signPlain,string time, string secretKey)
        {
            if (string.IsNullOrEmpty(time)||string.IsNullOrEmpty(requestSign)||string.IsNullOrEmpty(signPlain))
            {
                return false;
            }
            //is in range
            var now = DateTime.Now;
            long requestTime =0;
            if (long.TryParse(time,out requestTime))
            {
                var max = now.AddMinutes(5).ToString("yyyyMMddHHmmss");
                var min = now.AddMinutes(-5).ToString("yyyyMMddHHmmss");
                if (!(long.Parse(max) >= requestTime && long.Parse(min) <= requestTime))
                {
                    return false;
                }
              
            }
            else
            {
                return false;
            }

            //hashmac
            var sign = Encryption.HmacSHA256(secretKey, signPlain);

            return requestSign.Equals(sign, StringComparison.CurrentCultureIgnoreCase);
        }

 [TestMethod()]
        public void GetUserTest()
        {
            string url = "http://localhost:8090/api/test/GetUser";
            string userId = "A39891D4-6CEF-4538-A562-3A422CA9C17A";
            string appId = "100001";
            string secretKey = "M/vkPOWXgBa7GnRd73t7j+jsKfbZtb+f";
            string rumdon = Guid.NewGuid().ToString();
            string time = DateTime.Now.ToString("yyyyMMddHHmmss");

            //make signture plain text
            var sortDict = new SortedDictionary<string, string>()
            {
                {"userId",userId }
            };
            var signPlain = new StringBuilder();
            foreach (var keyValue in sortDict)
            {
                signPlain.AppendFormat("{0}={1}&", keyValue.Key, keyValue.Value);
            }
            if (signPlain.Length > 1)
            {
                //remove last &
                signPlain.Remove(signPlain.Length - 1, 1);
            }
            signPlain.Append(time);
            signPlain.Append(random);

            Console.WriteLine("sign plain:{0}", signPlain.ToString().ToUpper());
            //make sign
            var sign = Encryption.HmacSHA256(secretKey, signPlain.ToString().ToUpper());
            Console.WriteLine("sign:{0}", sign);

            string requestUrl = string.Format("{0}?{1}={2}", url, "userId", userId);
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(requestUrl);
            request.Method = "GET";
            //add headers
            request.Headers.Add("time", time);
            request.Headers.Add("appId", appId);
            request.Headers.Add("random", random);
            request.Headers.Add("sign", sign);
            //
            //start request
            try
            {
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {
                    var responseStream = response.GetResponseStream();
                    if (responseStream != null)
                    {
                        using (StreamReader reader = new StreamReader(responseStream))
                        {
                            var content = reader.ReadToEnd();

                            Console.WriteLine(content);
                        }
                    }
                }
            }
            catch (WebException ex)
            {
                using (HttpWebResponse response = (HttpWebResponse)ex.Response)
                {
                    var responseStream = response.GetResponseStream();
                    if (responseStream != null)
                    {
                        using (StreamReader reader = new StreamReader(responseStream))
                        {
                            var content = reader.ReadToEnd();
                            Console.WriteLine(content);
                        }
                    }
                }
            }
        }