protected function hashEquals($a, $b) {
		if (function_exists('hash_equals')) {
			return hash_equals($a, $b);
		}
		
		$nonce = openssl_random_pseudo_bytes(32);
		return hash_hmac($this->hashAlgo, $a, $nonce) === hash_hmac($this->hashAlgo, $b, $nonce);
	}