Authorization: VWS {provision_access_key}:{Signature}

Signature = Base64(HMAC-SHA1(server_secret_key, StringToSign ) ) ;
StringToSign =
  HTTP-Verb + "n" +
  Content-MD5 + "n" +
  Content-Type + "n" +
  Date + "n" +
  Request-Path;

class SignatureBuilder
    {
        public string tmsSignature(HttpWebRequest request, string seckretKey)
        {

            string method = request.Method;
            string ContentType = "";
            string HexDigest = "d41d8cd98f00b204e9800998ecf8427e";
            if (method.Equals("GET", StringComparison.OrdinalIgnoreCase) || method.Equals("DELETE", StringComparison.OrdinalIgnoreCase))
            { }
            else if (method.Equals("POST", StringComparison.OrdinalIgnoreCase) || method.Equals("PUT", StringComparison.OrdinalIgnoreCase))
            {
                ContentType = "application/json";
                HexDigest = contentMD5(request);
            }
            else
            { System.Console.WriteLine("Error: invalid content type passed to Sig Builder"); }
            string dateValue = request.Date.ToUniversalTime().ToString();
            string requestPath = request.RequestUri.ToString();
            string toDigest = method + "n" + HexDigest + "n" + ContentType + "n" + dateValue + "n" + requestPath;
            string shaHashed = "";
            try
            {
                shaHashed = CalculateRFC2104HMAC(seckretKey, toDigest);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            return shaHashed;
        }

        private string contentMD5(HttpWebRequest request)
        {
            const int BUFFER_MAX_SIZE = 1024;
            byte[] buffer = new byte[BUFFER_MAX_SIZE];
            using (Stream stream = request.GetRequestStream())
            {
                stream.Write(buffer, 0, BUFFER_MAX_SIZE);
            }
            string resultHash = BitConverter.ToString(MD5.Create().ComputeHash(buffer)).Replace("-", String.Empty).ToLower();
            return resultHash;
        }
        public static string CalculateRFC2104HMAC(string key, string data)
        {

            UTF8Encoding utf8 = new UTF8Encoding();
            string result = "";
            byte[] buffer = new byte[256];
            try
            {
                MemoryStream stream = new MemoryStream(buffer);
                stream.Write(utf8.GetBytes(data), 0, data.Length);
                var crypto = HMACSHA1.Create();
                crypto.Key = Encoding.UTF8.GetBytes(key);
                var buff = crypto.ComputeHash(buffer);
                result = BitConverter.ToString(buff).ToLower().Replace("-", string.Empty);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            return result;
        }
    }