[westurner]

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?

[jre]

Thanks for the precision regarding the hash.

Regarding the error, they are logged when a verify_block/transaction returns False, just to be a bit more explicit about what failed. In a real implementation, I guess you would throw exceptions instead (or use some Result pattern), but I tried and it cluttered the code quite a bit, so I went back to logging.

[westurner]

My mistake, it's BitTorrent that has a DHT. Instead of finding the most network local peer with the block identified by a (prev_hash, hash) hash table key, the Bitcoin blockchain broadcasts all messages to all nodes; which must each maintain a complete backup of the entire blockchain.

"Protocol documentation" https://en.bitcoin.it/wiki/Protocol_documentation