21 votes

How Banksy Authenticates His Work

10 comments

  1. [7]
    teaearlgraycold Link
    It seems to me that the note itself is useless here. All that matters is that there is an official source that can tell you what item (identified by a number) is owned by what person - and all...

    It seems to me that the note itself is useless here. All that matters is that there is an official source that can tell you what item (identified by a number) is owned by what person - and all changes of hands are communicated to this authority so they should know who owns what at any given time.

    The uniqueness of the tear isn't important, the amount of entropy in the ID isn't important. Just the privately held ledger.

    5 votes
    1. vektor Link Parent
      The article is vague on the details, but the whole asymmetric cryptography thing they're alluding to is pretty powerful. Your authoritative source is worthless if someone could "hijack" it, so...

      The article is vague on the details, but the whole asymmetric cryptography thing they're alluding to is pretty powerful. Your authoritative source is worthless if someone could "hijack" it, so they're putting all the digital eggs in one digital basket: Their private key. That's Banksy now. That's his ID. What you could do (not sure if in fact, but plausible by the article) is that they sign the document with it (the result is the number on the note) and publish their public key. Now everyone knows that that document was in fact signed by Banksy (or whoever holds the private key). No one else can do it because you can't get to the private key. At the same time, because he published his public key, everyone else can check that it was in fact him. You need the public key to check a signature and the private key to create one.

      But what about someone who just copies the number on the note? Sure, that'd work, but it'd only work for that particular print. That number might well sign for all the other information on the document.

      But of course, in that case there's nothing certifying that the identical copy of an original is not in fact the original. Some ledger here is needed. Truthfully though, it could be distributed, blockchain, centralized, whatever. If every art gallery recorded all the ownership transfers and verified the keys, that'd make it very hard to sneak in a copy, because the duplicates would show up. But even that doesn't help if I buy an original, duplicate it and it's certificate and then sell the duplicate, keeping the original. Everyone might think I sold the original. As far as I can tell, nothing can really help you out here, unless you can design a test that actually tells the two apart reliably - assuming some flaw in the copying process.

      1 vote
    2. [5]
      acdw Link Parent
      I thought the uniqueness was important because it made it harder to forge? Only the torn half on the true certificate would match the half in the vault.

      I thought the uniqueness was important because it made it harder to forge? Only the torn half on the true certificate would match the half in the vault.

      1. [4]
        teaearlgraycold Link Parent
        That provides some security, but it's trumped by the private ledger. Just printing the number on the paper would be enough. But if it's common for people to exchange Banksy's artwork without...

        That provides some security, but it's trumped by the private ledger. Just printing the number on the paper would be enough.

        But if it's common for people to exchange Banksy's artwork without informing Pest Control of the change of ownership then the bill is a good backup.

        3 votes
        1. [3]
          acdw Link Parent
          I think the ledger and note work together. The ledger keeps track of who's supposed to own the art, and has a history of owners, but the bill confirms that the owners are who they say they are. As...

          I think the ledger and note work together. The ledger keeps track of who's supposed to own the art, and has a history of owners, but the bill confirms that the owners are who they say they are. As the author of the article says:

          The tear is what uniquely separates the private key, the half of the note kept secret under lock and key at Pest Control, with the public key. The public key is the half of the note attached to the authentication certificate which gets passed on with the print, and allows its authenticity to be easily verified.

          We have no idea what has been written on Pest Control’s private half of the note. Which means it can’t be easily recreated, and that empowers Pest Control to keep the authoritative list of who currently owns each authenticated Banksy work.

          So the note is a good first-line of defense against forgery: someone would have to forge the artwork and the exact tear in the note which would match the other half kept by Pest Control, and if they managed to do this, Pest Control would contact the previous owners from the ledger to ask if they'd transferred the art to the forgers.

          So I guess I'm saying, I think the ledger serves as backup for the note, not the other way around.

          1. [2]
            zydeco Link Parent
            I'm thinking that if looked at under a microscope, which I would expect Pest Control has, it would be virtually impossible to duplicate a tear, fiber by fiber, especially since the pattern of...

            I'm thinking that if looked at under a microscope, which I would expect Pest Control has, it would be virtually impossible to duplicate a tear, fiber by fiber, especially since the pattern of fibers extending back away from the tear would also have to match up, but maybe someone dedicated enough will figure it out. Maybe some wag will decide that their conceptual art is fucking up Banksy's system.

            It does seem a bit weird and humorously dissonant that, considering Banksy's insistence on his own anonymity, his works in private hands are tracked in a master database of chain-of-provenance: the exact opposite of anonymity. Any work which loses or has altered its certificate, or maybe gets inherited or otherwise transferred without notification to Pest Control, someone in the chain dies, might result in a genuine piece losing its 'authenticity', and so, its validity and value. Maybe this is simply a necessary evil, but maybe the irony also amuses Banksy.

            1 vote
            1. acdw Link Parent
              I hadn't thought of the irony of Banksy's anonymity requiring the non-anonymity of all the owners of his art. I wonder if that see-saw of anonymity expands to other realms as well, for example...

              I hadn't thought of the irony of Banksy's anonymity requiring the non-anonymity of all the owners of his art. I wonder if that see-saw of anonymity expands to other realms as well, for example with public-key cryptography or everyone's favorite buzzword, blockchain tech.

  2. [3]
    mrbig Link
    Interesting comment. I know nothing about Banksy, but there's no way a man wouldn't be bragging about it to people :P

    Interesting comment. I know nothing about Banksy, but there's no way a man wouldn't be bragging about it to people :P

    2 votes
    1. [2]
      Hypersapien Link Parent
      Why? Not every male in the world adheres to your stereotypes.

      Why? Not every male in the world adheres to your stereotypes.

      3 votes
      1. mrbig Link Parent
        Of course not. That was a joke.

        Of course not. That was a joke.