Thanks! Simplest explanation I've seen.

Here's an nbviewer link (which, like base58, works on/over a phone): https://nbviewer.jupyter.org/github/julienr/ipynb_playground...

Note that Bitcoin does two rounds of SHA256 rather than one round of MD5. There's also a "P2P DHT" (peer-to-peer distributed hash table) for storing and retrieving blocks from the blockchain; instead of traditional database multi-master replication and secured offline backups.

> ERROR:root:Invalid transaction signature, trying to spend someone else's money ?

This could be more specific. Where would these types of error messages log to?