There's no explanation about how this is meant to work, either in the article on on Blockverify's website.
e.g. authenticating paintings: 1) Why should I trust the data in some blockchain to tell me whether or not the painting in my hands is genuine? and 2) How do I know in the first place that the data relates to this actual painting?
I can't see the magical step that can give reliable answers here.
That's because there is none. There's at least 5 different groups that got VC funding for the exact same idea, and it's all impossible and illogical. It doesn't even pass a sniff test so I've no idea how they managed to get millions of dollars for the concept.
I don't know if you can tie anything to a physical painting, but you can keep track of ownership through the ledger. I don't really know what this company has planned, but if you start at the source use the shared ledger to pass on ownership, then someone can prove that they own something.
Basically like a title being passed around on the blockchain.
I'm not saying the idea makes sense, but if you assume that the original owner announces the creation of the painting on the blockchain (we know this is legit because the owner has posted their public key in the past) and every legitimate transaction posts it to the blockchain, then:
If you steal the key, the painting is legally yours. Congratulations! You may send the police to collect your prize.
If you steal the painting, everyone you try to sell it can verify that you're not the real owner. That limits you to black market transactions, I guess.
If there are two claims for the same painting, it's trivial to trace them back to their source and see which one goes back to the original owner.
You prove thing == key by means of a perfect, tamper-proof sticker, which I'm sure someone will invent any day now.
You prove there aren't two keys by looking at the original owner's postings to the blockchain and making sure he hasn't listed the item twice.
If you lose the key, you can never sell the painting legally. At first I thought you could just invalidate the old key and assign a new one, but how can you do that in a tamper-proof way without access to the old private key? I guess if my identity is a separate key, I could post a message saying, "This is X, you know it's really me because here's my digital signature, you can verify that on this date I owned the thing, and I'm telling you to stop using public key Y for it and to use public key Z instead." Now there are two keys, and we have to assume the technology is good enough that no one could be tricked into using the old key; otherwise, I could sell the painting twice.
The real problem is definitely proving that thing == key. Once you have that, you have a system which kinda works (but is in every way worse than just using whatever tamper-proof technology it relies on for a title / certificate of authenticity, as joosters points out).
The only clue on their website seems to be 'Each product is labelled with Block Verify tag', but this in itself is useless:
* How can I tell that the label is genuine? With expensive items, an attacker can spend a lot of money creating an exact replica of a label. There's no hologram/anti-tamper system that's undefeatable.
* If we assume that Block Verify's tags are trustworthy and tamper-proof, and there's no way they could be duplicated or placed on to a fraudulent item, then at this point we don't actually need a blockchain to prove anything, as the label is proof enough.
It's just completely absurd. See how often and in such large amounts Bitcoin is stolen, and tell me that wouldn't happen with these keys as well. I get the impression there's just a lot of people getting VC money for complete and utter bullshit like this, and somehow employing a team of people for a concept that doesn't even make sense on a flashy website let alone in the real world.
e.g. authenticating paintings: 1) Why should I trust the data in some blockchain to tell me whether or not the painting in my hands is genuine? and 2) How do I know in the first place that the data relates to this actual painting?
I can't see the magical step that can give reliable answers here.