Segments API auth issue with node.js client

Hi,
I'm facing an authorization issue trying to use Segments APIs via a node.js client.

Stop beating around the bush, below the part of it which manages the POST request and the authorization via the x-wsse headers:

var now = new Date();

var options = {

     method: "POST",

     hostname: "api3.omniture.com",

     path: "/admin/1.4/rest/?method=Segments.Get",

     json: true,

     headers: {

            "Content-Type": "application/json",

            "Content-Length" : Buffer.byteLength(JSON.stringify(body)),

            "x-wsse": 'UsernameToken Username="[username]:[company]", PasswordDigest="xxxxxxxxxxxxxxxxxxxxxxxxxx==", Nonce="yyyyyyyyyyyyyyyyyyyyyyyyyy", Created="'+now+'"'

     }

};

As you see, I'm trying to replicate the x-wsse generated by the API Explorer, dynamically specifying the Created timestap via Date() JS class.

Node client is reporting me this error:

"{"error":"Bad Request","error_description":"Unable to validate authentication.","error_uri":null}"

I suppose the x-wsse PasswordDigest and Nonce values also continuously change at every request while here I put them static.

If this was the reason for the issue, how dynamically insert also those parameters in the x-wsse header ?

Thanks a lot.