[qqii]

A signature is simply that, a signature. It doesn't guarantee uniqueness and doesn't prevent you copying it any number of times.

An identity + timestamping mechanism would guarantee uniqueness of ownership, and a blockchain performs this in a relatively decentralised and trustless manner.

[stagas]

The blockchain sounds very centralised if it's the only place I can participate to verify my ownership. Decentralised would be if there was no third party(in this case the blockchain) necessary for verifying ownership. Which it actually isn't, because all that is needed is the signature of the author and maybe a timestamp or some other metadata signed along.

[qqii]

Of course! The blockchain is only decentralised compared to a centralised service such as Sotheby's and doesn't remove the third party entirely. The thing is unless you restrict the requirements of the artwork and the transaction not involving a third party actually restricts future guarentees that can be made to third parties.

If the restrictions of never involving third parties (in proofs of ownership or otherwise) is acceptable, then there's no need for any schema bar making the transaction itself.

The issue with removing the third party entirely (as the auther suggests) is the verifiability of the timestamp to any interested third parties. The simplest scenario is proof of existence of the artwork at time T. Without a timestamping mechanism there's nothing stopping the creator lying about when it was created, or when this transaction took place.