in js/plugins/ajax-contact-extend/classes/twitter/EpiOAuth.php [188:200]
protected function signString($string = null)
{
$retval = false;
switch($this->signatureMethod)
{
case 'HMAC-SHA1':
$key = $this->encode($this->consumerSecret) . '&' . $this->encode($this->tokenSecret);
$retval = base64_encode(hash_hmac('sha1', $string, $key, true));
break;
}
return $retval;
}