Kademlia: A Peer-To-peer Information System Based on the XOR Metric (2002) [pdf]
I love how people are rediscovering the previous generation of P2P software from 15-20 years ago.  Reading through these papers was a huge part of my college procrastination; maybe now that cryptocurrencies give a way to provide economic incentives to those who contribute computing power, we might see a renaissance of some of these older ideas.