# Block Chain and Bitcoin The main ideas, seen below, are: * Digital signatures * The ledger is the currency * Decentralize * Proof of work * Block Chain ![](Screen%20Shot%202021-04-27%20at%208.48.43%20AM.png) --- References: * [But how does bitcoin actually work](https://www.youtube.com/watch?v=bBC-nXj3Ng4) * [Robert Breedlove: Philosophy of bitcoin from first principles](https://www.youtube.com/watch?v=HrehEWYj16s&t=8045s)