Almost everything you read about the blockchain is wrong. No new technology since the Internet itself has excited so many pundits, but blockchain just doesn’t do what most people seem to think it does. We’re all used to hype, and we can forgive genuine enthusiasm for shiny new technologies, but many of the claims being made for blockchain are just beyond the pale. It's not going to stamp out corruption in Africa; it's not going to crowdsource policing of the financial system; it's not going to give firefighters unlimited communication channels. So just what is it about blockchain?
The blockchain only does one thing (and it doesn’t even do that very well). It provides a way to verify the order in which entries are made to a ledger, without any centralized authority. In so doing, blockchain solves what security experts thought was an unsolvable problem – preventing the double spend of electronic cash without a central monetary authority. It’s an extraordinary solution, and it comes at an extraordinary price. A large proportion of the entire world’s computing resource has been put to work contributing to the consensus algorithm that continuously watches the state of the ledger. And it has to be so, in order to ward off brute force criminal attack.