Creating A Service Bus SAS Token and Consuming Relay in WinRT

Question

I have a Service Bus Relay (WCF SOAP) I want to consume in my Windows Store App. I have written the code to create a token as well as the client which is below.
The problem is that I get an AuthorizationFailedFault returned with a faultstring "InvalidSignature: The token has an invalid signature." And I can't figure it out.
My Create Token method:
private static string CreateSasToken()
TimeSpan sinceEpoch = DateTime.UtcNow - new DateTime(1970,1, 1);
var expiry = Convert.ToString((int)sinceEpoch.TotalSeconds + 3600);
string stringToSign = webUtility.UrlEncode(ServiceUri.AbsoluteUri) + "\n" + expiry;
string hashKey = Encoding.UTF8.GetBytes(Secret).ToString();
MacAlgorithmProvider macAlgorithmProvider = MacAlgorithmProvider.OpenAlgorithm(MacAlgorithmNames.HmacSha256);
BinaryStringEncoding encoding = BinaryStringEncoding.Utf8;
var messageBuffer = CryptographicBuffer.ConvertStringToBinary(stringToSign,encoding);
IBuffer keyBuffer = CryptographicBuffer.ConvertStringToBinary(hashKey,encoding);
CryptographicKey hmacKey = macAlgorithmProvider.CreateKey(keyBuffer);
IBuffer signedMessage = CryptographicEngine.Sign(hmacKey, messageBuffer);
string signature = CryptographicBuffer.EncodeToBase64String(signedMessage);
var sasToken = String.Format(CultureInfo.InvariantCulture,
"SharedAccessSignature sr={0}&sig={1}&se={2}&skn={3}",
WebUtility.UrlEncode(ServiceUri.AbsoluteUri),
WebUtility.UrlEncode(signature), expiry, Issuer);
return sasToken;
My Client class:
public partial class ServiceClient
public async Task<string> GetDataUsingDataContract(string item, string sasToken)
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Add("ServiceBusAuthorization",sasToken);
client.DefaultRequestHeaders.Add("SOAPAction",".../GetDataUsingDataContract");
client.DefaultRequestHeaders.Add("Host", "xxxxxxxxxxx.servicebus.windows.net");
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post,ServiceUri);
var content =new StringContent(@"<s:Envelope
xmlns:s=""http://schemas.xmlsoap.org/soap/envelope/"">
<s:Header></s:Header><s:Body>"+ item +@"</s:Body>
</s:Envelope>",System.Text.Encoding.UTF8,"application/xml");
request.Content = content;
HttpResponseMessage wcfResponse = client.SendAsync(request).Result;
HttpContent stream = wcfResponse.Content;
var response = stream.ReadAsStringAsync();
var returnPacket = response.Result;
return returnPacket;
I have been successful consuming the Relay using Http (via Fiddler) by copying an unexpired token created by Micorosft.ServiceBus in a console app.
John Donnelly

Answer 1

Thanks Girish. I eagerly await some help on this. I have figured a lot out but I am stuck on creating a good SAS Token.
I reposted a question I asked on StackOverflow here  in this MSDN forum
here if you can help on creating steer me in the right direction.
John Donnelly