Dmitri's description of a notary is inaccurate under existing law.

A notary could act as a TTP "plus" in that secure recordation of the time would be one essential component of the act of notarization, but the statement that the notary "checks the digital signatures" is not supported by current statutes. The notary is required by Anglo American law to check identity and the voluntariness of the act of signing, but not the signature of the signer. Moreover, there is no requirement of a digital signature of a signer, either in theory, or in the policies of the entities who are effectuating the infrastructure for online mortgage and title transactions, and sworn statements suitable for court.

The model most commonly mentioned allows the requestor to sign using any method he or she chooses, which is cryptographically bound to a transaction by the digital signature of the notary. This comes very close to the requestor use case, unless the notary is also required to witness the act of signature of the requestor which is affixed in the presence of the notary, as is the case in the paper world.