function _rsassa_pss_verify($m, $s)
    {
        // Length checking

        if (strlen($s) != $this->k) {
            user_error('Invalid signature');
            return false;
        }

        // RSA verification

        $modBits = 8 * $this->k;

        $s2 = $this->_os2ip($s);
        $m2 = $this->_rsavp1($s2);
        if ($m2 === false) {
            user_error('Invalid signature');
            return false;
        }
        $em = $this->_i2osp($m2, $modBits >> 3);
        if ($em === false) {
            user_error('Invalid signature');
            return false;
        }

        // EMSA-PSS verification

        return $this->_emsa_pss_verify($m, $em, $modBits - 1);
    }