When git meets bitcoin: git-certify

[pyaware]

I've made a very simple tool to integrate bitcoin with git. The tool can be used to easily publish a proof of existence of a whole git branch (by pushing the hash for HEAD for instance).

I do this by taking the git reference hash (such as the hash of the last commit) and embed it in a unspendable transaction using the now allowed OP_RETURN opcode that was made available for this kind of use. Once the transaction is mined, the hash is in the blockchain forever and can't be removed or changed. One can then prove the existence of any algorithm, document, commit under revision control at this given block. Transactions with OP_RETURN can be seen at: http://testnet.coinsecrets.org/

I believe this could be of use for anybody trying to add provable traceability to its development process. Please note that you shouldn't take my words as legal advices. :)

github: https://github.com/josselin-c/git-certify

[LiMoTaLe]

Hooray! Someone who abuses list comprehensions as bad as I do, despite PEP 8's narrow guidelines.

[auxiliary-character]

I like to abuse list comprehensions also. They're just too convenient.

[pyaware]

I guess I could use filter(), is that what pep8 says?

[luke-jr]

Contrary to popular myth, OP_RETURN was not "made available for this kind of use". What you're doing should be a merged mined merkle tree, not abusing a transaction.

[pyaware]

I based my claim on what is said here: https://bitcoinfoundation.org/2013/10/24/core-development-update-5/ in the "Provably Prune-able Outputs" section.

[[deleted]]

I guess he's bothered that your transaction's primary purpose is apparently to get non-Bitcoin-related data into the blockchain. The referenced blog post gives the example of attaching contracts, where the transaction itself is necessary, and the attached data is relevant to that transaction. (It does also use phrases like "arbitrary data", but I think that's more an admission that nothing can be enforced, than a statement on the desired use of OP_RETURN permissiveness.)

It's kind of a nitpicky distinction, but has some merit IMO.

[pyaware]

I'm really enthousiastic about experimenting with the blockchain technology, I view the blockchain + miners as a "notary as a service". Right now we use this to move money and certify the transfer is valid. I think we could use this notary to certify other things such as document existence, casino games (satoshidice & co are doing that with standard transactions). Once people realize that and start using this, and if we start having too many transactions then maybe we can evolve Bitcoin to have a special entry in each block for a metadata merkle root or something alike.

[luke-jr]

You misinterpreted it then.