Lewis spent about a third of the book on the history of money and how money works with central banks and exchanges. This was good because as a programmer I know about the encryption and distributed nodes part of cryptocurrency; I just didn't understand how it could be money. I like buying things with cash, simple, anonymous but not digital. Crypto is an attempt to make a digital version of cash where there is no intermediary, like a bank. Transactions are between individuals with no central control or transaction monitoring. I reviewed my knowledge of hashing and public-private key encryption, learned about block-chain ledger. The design of the BitCoin network of thousands of nodes all copying transactions into blocks and adding them onto a block-chain is mind numbingly complicated probably by necessity because everyone is verifying transactions and building blocks at the same time according to a strict protocol but with no outside-the-system verification. So the protocol and the software are controlled by a few people, but the participants are equal and anonymous. The value of BitCoins and other crypto currency is volatile, so that at present it is best thought of as a digital asset rather than money, but I can see how it might be the money of the future if they can overcome the excessive power required to mine it. I don't know how far away quantum computing is, but when that arrives, encryption may have to be rethought as a way to secure things. BitCoin Exchanges trade fiat currency for crypto and take a fee. That must be how Trump's crypto grift works.

If it's subversive, I'm in. Great Bill McKibben quote: "If you want to upend the balance of political and economic power on this earth—and we should, because grotesque inequality is deeply wrong—then there is no place better to start than by changing the way we make electrical power. Turning to the heavens for our energy instead of to hell is a profoundly subversive act."