Proof of existence is a new online service that aims to provide a novel use for the Bitcoin blockchain. Rather than being a way to transfer funds, the service provides a way to prove when a file came into existence. Could this be a way to reduce to copyright system down into an algorithm in the same way that Bitcoin has done with finance?
Copyright has always been a controversial subject, but even more so in the age of the Internet. Even before copyright can be enforced, a court must determine who was the original creator of the work in question. Proving who came first can be a complicated subject. As stated on CoinTelegraph,
According to U.S. Copyright Office, a copyright is formed the moment a work is created and fixed in a tangible form that is perceptible either directly or with the aid of a machine or device.
However, the technology of the Bitcoin blockchain could provide a way to make such cases clearer, if the “Proof of Existence” service has anything to do with it.
As stated on its website,
Use our service to anonymously and securely store an online distributed proof of existence for any document. Your documents are NOT stored in our database or in the bitcoin blockchain, so you don’t have to worry about your data being accessed by others.
All we store is a cryptographic digest of the file, linked to the time in which you submitted the document. In this way, you can later certify that the data existed at that time. This is the first online service allowing you to publicly prove that you have certain information without revealing the data or yourself, with a decentralized certification based on the bitcoin network.
The technical underpinnings of Proof of Existence relies upon sending special codes into the blockchain, in exchange for a trivial amount (5 mBTC) of bitcoin. The block for this transaction also contains a SHA256 hash of the uploaded file into the blockchain, via the OP_RETURN bitcoin scripting opcode. This script marks the transaction output as “provably unspendable“. The developer also states that additional data is added to the hash to mark the block as having been created by his service.
What Proof of Existence offers is clearly useful – for a given blob of data, it’s possible to prove when it was created. As with any Bitcoin transaction, the ownership is anonymous. However, as with any Bitcoin transaction, the input and output addresses are saved. So as long as someone can prove ownership of an address (e.g. by signing a message with the private key), they can prove ownership of the original file.
By the nature of cryptographic hashing, any small change in a file can have a massive effect on value of the hash. Therefore, someone could make a minor change to a file and pass it off as something new. However, if all versions of a disputed piece of content are available, then the hashes can be checked against Proof of Existence. Then, the file corresponding to the earliest notary date can be regarded as the original version.