Hautelook\Phpass\PasswordHash::crypt_private PHP Method

    public function crypt_private($password, $setting)
    {
        $output = '*0';
        if (substr($setting, 0, 2) == $output) {
            $output = '*1';
        }
        $id = substr($setting, 0, 3);
        # We use "$P$", phpBB3 uses "$H$" for the same thing
        if ($id != '$P$' && $id != '$H$') {
            return $output;
        }
        $count_log2 = strpos($this->itoa64, $setting[3]);
        if ($count_log2 < 7 || $count_log2 > 30) {
            return $output;
        }
        $count = 1 << $count_log2;
        $salt = substr($setting, 4, 8);
        if (strlen($salt) != 8) {
            return $output;
        }
        // We're kind of forced to use MD5 here since it's the only
        // cryptographic primitive available in all versions of PHP
        // currently in use.  To implement our own low-level crypto
        // in PHP would result in much worse performance and
        // consequently in lower iteration counts and hashes that are
        // quicker to crack (by non-PHP code).
        if (PHP_VERSION >= '5') {
            $hash = md5($salt . $password, TRUE);
            do {
                $hash = md5($hash . $password, TRUE);
            } while (--$count);
        } else {
            $hash = pack('H*', md5($salt . $password));
            do {
                $hash = pack('H*', md5($hash . $password));
            } while (--$count);
        }
        $output = substr($setting, 0, 12);
        $output .= $this->encode64($hash, 16);
        return $output;
    }