8. Other possible blockchains

The general definition of a blockchain could be: a blockchain is a file (a) shared on a peer-to-peer network (i.e., reproduced and stored at each node), (b) secured by good cryptographic primitives, (c) which evolves only under the control of a community with an interest in its existence, (d) where nothing is erased, and (e) which expands its content by periodically adding pages chained together. It's a sure-fire way of sharing information and building trust between distant players, who may not even know each other.

Satoshi Nakamoto invented and cleverly put this idea into practice, giving it a particular, open implementation: new players can join in at any time, others can withdraw, everything is public and nothing is encrypted. However, creating decentralized digital currencies is not the only use that can be made of this type of software construction based on...