SharedAccessSignature Azure

Question

I'm trying to provide 'read-only' access for my blobs via a Web Service. The Web Service has a method that takes in the Blob and Container information and then returns back a URL with the Shared Access Signature that the user can use to access the blob.
Since these images (blobs) are cached on the Phone, I would like to keep the signatures valid for up to 1 day.
I am using the following code:
var blobClient = GetBlobClient();
var container = blobClient.GetContainerReference(containerName);
if (container != null)
container.CreateIfNotExist();
var policy = new SharedAccessPolicy()
SharedAccessStartTime = DateTime.Now,
Permissions = SharedAccessPermissions.Read,
SharedAccessExpiryTime = DateTime.Now.AddDays(days)
if (permissions.Contains("w"))
policy.Permissions = policy.Permissions | SharedAccessPermissions.Write;
policy.SharedAccessExpiryTime = DateTime.Now.AddMinutes(10);
//The shared access policy provides read/write access to the container for 10 hours.
BlobContainerPermissions containerPerms = new BlobContainerPermissions();
// The public access setting explicitly specifies that the container is private,
// so that it can't be accessed anonymously.
containerPerms.PublicAccess = BlobContainerPublicAccessType.Off;
containerPerms.SharedAccessPolicies.Clear();
containerPerms.SharedAccessPolicies.Add("mypolicy", policy);
// Set the permission policy on the container.
container.SetPermissions(containerPerms);
var blob = container.GetBlobReference(blobName);
// Get the shared access signature to share with users.
var blobPolicy = new SharedAccessPolicy();
blobPolicy.SharedAccessExpiryTime = DateTime.Now.AddDays(days);
blobPolicy.Permissions = SharedAccessPermissions.Read;
string sas = blob.GetSharedAccessSignature(blobPolicy, "mypolicy");
return sas;
Every time I try to use this code, I get the following error: Signature did not match. String to sign used was r 2012-01-03T08:38:52Z /myContainer/12100/12409/29cae1b6-2955-4a33-ab27-ff99f0bb6470_m.jpg mypolicy
Can anyone please guide me with this?

Answer 1

I think you may refer to this 
http://msdn.microsoft.com/en-us/library/windowsazure/hh508996.aspx