Talk of blockchain technology is everywhere, it seems, thanks to the rise of Bitcoin and other cryptocurrencies—but what is it, and what does it do?
1. Don’t call it “the” blockchain
The first thing to know about the blockchain is, there isn’t one: there are many. Blockchains are distributed, tamper-proof public ledgers of transactions. The most well-known is the record of bitcoin transactions, but in addition to tracking cryptocurrencies, blockchains are being used to record loans, stock transfers, contracts, healthcare data and even votes.
2. Security, transparency: the network’s run by us
There’s no central authority in a blockchain system: Participating computers exchange transactions for inclusion in the ledger they share over a peer-to-peer network. Each node in the chain keeps a copy of the ledger, and can trust others’ copies of it because of the way they are signed. Periodically, they wrap up the latest transactions in a new block of data to be added to the chain. Alongside the transaction data, each block contains a computational “hash” of itself and of the previous block in the chain.
Hashes, or digests, are short digital representations of larger chunks of data.
Modifying or faking a transaction in an earlier block would change its hash, requiring