Access denied error: Services + Json Server + Cake PHP without SID: Not works...

Hi,

I need give access for a CakePHP App to the method "user.get", I have rewritten the user.get method to fetch the User by e-mail (ap_user.get).

The code is working very well using Session, however my CakePHP App don't have the Drupal Session info, only the API-Key for that I need to remove the "$sid" reference from my code:

global $user;
$webservice 	= 'http://localhost/services/json';
$api_key 		= '48afc1w3q3539000c6b14ec9fx3177ae';
$domain 		= $_SERVER['HTTP_HOST'];
$timestamp 		= (string) time();
$nonce 			= user_password();
$sid 			= $user->sid;
$method 		= 'ap_user.get';
$hash 			= hash_hmac('sha256', $timestamp.';'.$domain.';'.$nonce.';'.$method, $api_key);


$ch = curl_init();
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_URL, $webservice);

$data = array(
	'method'			=> '"'.$method.'"',
	'hash'				=> '"'.$hash.'"',
	'domain_name'		=> '"'.$domain.'"',
	'domain_time_stamp' => '"'.$timestamp.'"',
	'nonce' 			=> '"'.$nonce.'"',
//	'sessid'			=> '"'.$sid.'"',
	'mail'				=> '"foo@bar.com"'
);

curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
$result = curl_exec($ch);
var_dump($result);

- I have already unchecked the Session checkbox on Keys Settings
- I have granted access to the Anonymous user for user_services module.

However is still returning the following error:

string(77) "{ "#error": false, "#data": { "#error": true, "#message": "Access denied" } }" 

Note: dis-commenting the: // 'sessid' => '"'.$sid.'"', will make the code run perfectly! =(

Any ideas?
Thank you