function getAssociation($assoc_handle, $dumb, $check_expiration=true)
    {
        if ($assoc_handle === null) {
            return new Auth_OpenID_ServerError(null,
                                     "assoc_handle must not be null");
        }

        if ($dumb) {
            $key = $this->dumb_key;
        } else {
            $key = $this->normal_key;
        }

        $assoc = $this->store->getAssociation($key, $assoc_handle);

        if (($assoc !== null) && ($assoc->getExpiresIn() <= 0)) {
            if ($check_expiration) {
                $this->store->removeAssociation($key, $assoc_handle);
                $assoc = null;
            }
        }

        return $assoc;
    }