  Peer-to-peer (p2p) content delivery is promising to provide benefits like
cost-saving and scalable peak-demand handling in comparison with conventional
content delivery networks (CDNs) and complement the decentralized storage
networks such as Filecoin. However, reliable p2p delivery requires proper
enforcement of delivery fairness, i.e., the deliverers should be rewarded
according to their in-time delivery. Unfortunately, most existing studies on
delivery fairness are based on non-cooperative game-theoretic assumptions that
are arguably unrealistic in the ad-hoc p2p setting. We for the first time put
forth the expressive yet still minimalist securities for p2p content delivery,
and give two efficient solutions FairDownload and FairStream via the blockchain
for p2p downloading and p2p streaming scenarios, respectively. Our designs not
only guarantee delivery fairness to ensure deliverers be paid (nearly)
proportional to his in-time delivery, but also ensure the content consumers and
content providers to be fairly treated. The fairness of each party can be
guaranteed when the other two parties collude to arbitrarily misbehave.
Moreover, the systems are efficient in the sense of attaining asymptotically
optimal on-chain costs and optimal deliverer communication. We implement the
protocols to build the prototype systems atop the Ethereum Ropsten network.
Extensive experiments done in LAN and WAN settings showcase their high
practicality.
