Blockchain Toy

Inspired by @dvf's blog post Learn Blockchains by Building One, I decided to implement my own in ruby.

Features

Blockchain: the integrity of each block depends on that of the previous one. Uses SHA256.
Proof of Work: a block is mined by finding a nonce that results in a hash with 4 leading zeros.
Consensus: the longest blockchain wins.
Secure Transactions: they are signed using ECDSA with a private key held by the initiator, and verified by each node before they get added to the blockchain.
Wallets: addresses are derived from a SHA256 hash of the public key belonging to the wallet.
Peering: each node manually names peers. They communicate via a JSON API over HTTP.
UI: each node runs a web based dashboard.
Persistence: each node keeps a local cache of the full blockchain (blockchain.json) and it's wallet keys (wallet.json)

# requires ruby 2.4+
bundle install
PASSWORD=cucumber PORT=4567 ruby app.rb

Load the web UI at http://localhost:4567. Username is admin, password as above.