Fri, Apr 24, 2015
It’s surprisingly hard to find a pure and concise definition of a block chain. Wikpedia’s entry on Block chain (transaction database), now redirects to a small section of the Bitcoin entry. In “Mastering Bitcoin”, Andreas M. Antonopoulos describes a blockchain as “an ordered, back-linked list of blocks”. He further states, “Each block within the blockchain is identified by a hash, generated using the SHA256 cryptographic hash algorithm on the header of the block. Each block also references a previous block”.
Clearly, Bitcoin comes to mind when people talk about block chains, and innovators are excited about block chains beyond simple tokenized currency. One thing that comes up a lot is the topic of a permanent record.
The hash of the latest block in a block chain is a cryptographic guarantee of all the blocks that came before it.
I think I’ve seen this scheme before… in the popular version control system, “Git”. In Git, a SHA-1 hash is used to uniquely identify each commit.
Of course, there is no “proof of work” (PoW) in Git. PoW is what makes it expensive to overwrite history in Bitcoin. More specifically, PoW solves the problem of decentralized consensus in Bitcoin.
Millions of developers use Git on a daily basis and rely on commit hashes to create an ordered guarantee of history. However, Git users must manually choose who they trust to update commit changes.
However, imagine the following scenario:
- Thousands of transactions, or pieces of data are being recorded each second.
- All of that data can be committed to a Git repository. Perhaps data can be batched together into a single commit.
- After recording thousands of commits, each containing thousands of transactions, a single hash, such as “f883f426c6da861bb31c5b5d645e638d44cb2c1f” is published each day.
This hash guarantees the integrity of all of the commits in the Git repository. The hash could be tweeted, or even published in a newspaper, guaranteeing an ordered history of events.
Clearly Git has some blockchain-esqe properties. Should it be considered a fully fledged block chain? If so, I believe that would make Git, by far, the most widely used piece of block chain technology today, protecting far more value than all other block chains combined.
– Everett Forth (Tech Lead at Domus Tower)