Don't forget the costs of relying on authority. First, trust can be broken. Second, if notary is offline or asleep you cannot register your data. Also: even if

Don't forget the costs of relying on authority. First, trust can be broken. Second, if notary is offline or asleep you cannot register your data. Also: even if you fully trust your notary, it's no guarantee some random people in Japan, Australia or South America will trust him too. Anyone anywhere can verify blockchain, though.