向yobit api发帖子请求

Question

我正在尝试在UWP平台上向yobit api发帖请求，这些代码适用于其他平台。这是我的代码 -

public async Task<RootObject> sellLimitCode()
    {
        RootObject track = null;
        try
        {
            string url = "https://yobit.net/tapi/";


            string parameters = "method=Trade&pair=ltc_btc&type=buy&rate=1&amount=1&nonce=" + (int)(DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalSeconds;
            String strMsg = "api secret";
            var uriBytes = encoding.GetBytes(parameters);
            var uriBytes1 = encoding.GetBytes(strMsg);
            string str_alg_name = MacAlgorithmNames.HmacSha512;
            MacAlgorithmProvider obj_mac_prov = MacAlgorithmProvider.OpenAlgorithm(str_alg_name);
            IBuffer buff_msg = CryptographicBuffer.CreateFromByteArray(uriBytes);
            IBuffer buff_key_material = CryptographicBuffer.CreateFromByteArray(uriBytes1);
            CryptographicKey hmac_key = obj_mac_prov.CreateKey(buff_key_material);
            IBuffer hmac = CryptographicEngine.Sign(hmac_key, buff_msg);
            byte[] digest = hmac.ToArray();
            string hashText = byteToString(digest);
            StringBuilder hex1 = new StringBuilder(hashText.Length * 2);
            foreach (byte b in digest)
            {
                hex1.AppendFormat("{0:x2}", b);
            }
            string sign1 = hex1.ToString();
            var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

            httpWebRequest.Method = "POST";

            httpWebRequest.Headers["Key"] = "api key";
            httpWebRequest.Headers["Sign"] = sign1;
            httpWebRequest.ContentType = "application/x-www-form-urlencoded";



            var httpResponse = (HttpWebResponse)await httpWebRequest.GetResponseAsync();

            using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
            {
                var result = streamReader.ReadToEnd();

            }

        }
        catch (Exception ex)
        { }

        return track;

    }

但我获得了成功：0，无效的密钥，方法或nonce。我尝试过更改所有内容。但仍无法正常工作。