bitcoin (P2P electronic cash system)

Bitcoin is a free open source peer-to-peer electronic cash system
that is completely decentralized, without the need for a central
server or trusted parties.  Users hold the crypto keys to their
own money and transact directly with each other, with the help
of a P2P network to check for double-spending.

Bitcoin Core connects to the Bitcoin peer-to-peer network to
download and fully validate blocks and transactions.

Please make sure to read the release notes first before upgrading:
https://bitcoincore.org/en/releases/29.0/

zeromq is an optional dependency (autodetected).