function lookup_nonce($consumer, $token, $nonce, $timestamp)
{
$n = new Nonce();
$n->consumer_key = $consumer->key;
$n->ts = common_sql_date($timestamp);
$n->nonce = $nonce;
if ($n->find(true)) {
return true;
} else {
$n->created = DB_DataObject_Cast::dateTime();
$n->insert();
return false;
}
}