[rxp]

"Slow money" in Neptune's Brood is a digital currency, and is confusingly referred to as a "bitcoin" a few times, but it's actually a really fascinating idea that's very different from BTC.

The gist of it, if I remember it right, is that all transactions are authenticated by an interstellar 2-phase commit handshake. The distances involved keep the value of the currency stable, because transactions can take decades to process, and the direction of the signal is actually used as a form of authentication, to guard against (literal) MITM attacks. The goal of slow money was to have a currency that was stable enough to finance multi-century interstellar colonization projects.