How is that supposed to work? Blockchains are public, they don't keep secrets.
> then even if you get a copy of the asset you can't do anything with it without using the chain.
Sure can. Take the key off the public chain, put it on pastebin. Done.
> you can't replace it either because that would change the signature,
Sure can. Yeah, signatures may change. But that only matters to the extent that people do. The chain has no effect.
> and the owner can just reupload his original copy with the correct signature.
What owner? I still have no idea what you're envisioning here. What's this for? What purpose does it serve? How does it do that technically?
you can store encrypted data on the chain. if i sell you a movie, i can give you the encrypted movie and use your public key to store an encrypted message with the key to open the movie. that way i can use a smart contract on the chain to track if you opened the movie.
Yeah, signatures may change. But that only matters to the extent that people do. The chain has no effect.
if the signature is on the chain and the chain is used to verify your ownership claim, then how exactly does the chain have no effect?
What owner?
the owner of the digital asset. an NFT for example, let's ignore for a moment that NFTs are stupid. or a movie. the purpose that it serves is to track the ownership of an asset. sure, you can make a copy of it. but you don't own that copy. if i discover that you made a copy, i can charge you with theft (see piracy) because i'll use the chain as proof of ownership and i can prove that you don't own your copy.
i am not saying that we want this. i am not a fan of blockchains. but to my understanding this is how they can be used.
That's not going to work. Any encrypted material in the blockchain is public. Any algorithm in it is also public. So I can just execute the code by hand, skipping any tracking code.
> if the signature is on the chain and the chain is used to verify your ownership claim, then how exactly does the chain have no effect?
This is all contingent on everyone caring about what the chain says. If I get hold of the movie and the key, the chain may say you own the movie, but I don't care. Now what?
> the purpose that it serves is to track the ownership of an asset. sure, you can make a copy of it. but you don't own that copy.
Movies are sold by the millions. Is the idea here making a million different watermarked copies of any given movie? If so, the watermark is the important bit, so what do you want the blockchain for? Just point to the court that John Smith has a movie that was tagged as having been sold to Joe Bloggs, and thus isn't his.
> if i discover that you made a copy, i can charge you with theft (see piracy) because i'll use the chain as proof of ownership and i can prove that you don't own your copy.
1. I bet it's going to be fun to explain all the details of the blockchain to the court and to convince them that this is indeed a tight proof of ownership.
2. If the blockchain is the ultimate arbiter of who owns what, then as soon as I manage to hack you, I can steal all your stuff, become its rightful owner in the view of both the blockchain and the law, and then sue you.
