public function addTrustRoot($identity, $trustRoot) {
		assert('is_string($identity)');
		assert('is_string($trustRoot)');

		$trs = $this->getTrustRoots($identity);
		if (!in_array($trustRoot, $trs, TRUE)) {
			$trs[] = $trustRoot;
		}

		$this->saveTrustRoots($identity, $trs);
	}