Don't be spooked by the technobabble that people use to describe "blockchain." A blockchain is just a database. It isn't a particularly sophisticated one, either - you could create it in a spreadsheet with minimal effort. There are some peculiarities with these databases. The first is that blockchains are append-only. That means that you can only add information - you can't just click on a cell and delete stuff that you've already added, or change it in any way. The second...