hash value

In services_admin_browse.inc, the hash calculation doesn't match that in services.module.
hash_hmac("sha256", $timestamp . $_SERVER['HTTP_HOST'] . $nonce . arg(4), services_admin_browse_get_first_key()))
This can be verified by entering a user name and password at the service admin page of user.login

One more question, what is "#signed_parameter"? Sorry I am new to PHP. I found this in function services_validate_key and services_method_call. Currently I am calculating hash in Java following the C# example in the handbook(http://drupal.org/node/308629), which doesn't include any signed parameter in hash calculation. I am getting "invalid api key" error. Thanks.
sb.Append(timestamp);
sb.Append(";");
sb.Append(domain);
sb.Append(";");
sb.Append(nonce);
sb.Append(";");
sb.Append("user.login");