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Mobihoc '20 Conference Paper · Oct 2020

Rewarding Relays for Decentralised NAT Traversal using Smart Contracts

Navin V. Keizer · Onur Ascigil · Yiannis Psaras · George Pavlou

Traversing NAT's remains a big issue in P2P networks, and many of the previously proposed solutions are incompatible with truly decentralised emerging applications. Such applications need a decentralised NAT traversal solution without trusted centralised servers. In this paper we present a decentralised, relay-based NAT traversal system, where any reachable node is able to assist an unreachable node in NAT traversal. Smart contracts on the Ethereum blockchain are used to ensure fair rewards. Besides financial incentives, a reputation system based on transactions on-chain is used to mitigate against malicious behaviour, and guide peer discovery. Evaluation of our system shows that a combination of historic performance metrics leads to an optimal scoring function, that the system takes little time to reach stability from inception, and that the system is resilient against various attacks. Implementation of the smart contract shows that the cost for participants is manageable.

GossipSub: Attack-Resilient Message Propagation in the Filecoin and ETH2.0 Networks

Dimitris Vyzovitis · Yusef Napora · Dirk McCormick · David Dias · Yiannis Psaras

Permissionless blockchain environments necessitate the use of a fast and attack-resilient message propagation protocol for Block and Transaction messages to keep nodes synchronised and avoid forks. We present GossipSub, a gossip-based pubsub protocol, which, in contrast to past pubsub protocols, incorporates resilience against a wide spectrum of attacks. Firstly, GossipSub's mesh construction implements an eager push model keeps the fan-out of the pubsub delivery low and balances excessive bandwidth consumption and fast message propagation throughout the mesh. Secondly, through gossip dissemination, GossipSub realises a lazy-pull model to reach nodes far-away or outside the mesh. Thirdly, through constant observation, nodes maintain a score profile for the peers they are connected to, allowing them to choose the most well-behaved nodes to include in the mesh. Finally, and most importantly, a number of tailor-made mitigation strategies designed specifically for these three components make GossipSub resilient against the most challenging Sybil-based attacks. We test GossipSub in a testbed environment involving more than 5000 VM nodes deployed on AWS and show that it stays immune to all considered attacks. GossipSub is currently being integrated as the main messaging layer protocol in the Filecoin and the Ethereum 2.0 (ETH2.0) blockchains.

The InterPlanetary File System and the Filecoin Network

Yiannis Psaras · David Dias

The InterPlanetary File System (IPFS) is a peer-to-peer content-addressable distributed file system that seeks to connect all computing devices with the same system of files. It is an open-source community-driven project, with reference implementations in Go and Javascript, and a global community of millions of users. IPFS and libp2p, which is the modular network stack of IPFS, are based on name-resolution based routing. The resolution system is based on Kademlia DHT and content is addressed by flat hash-based names. IPFS sees significant real-world usage, with over 250,000 daily active network nodes, millions of end users and wide adoption by several other projects in the Decentralised Web space, but not only. An adjacent project to IPFS, which was also masterminded and is also being developed within Protocol Labs (the umbrella company of IPFS and libp2p) is filecoin. Filecoin is a token protocol that supports a decentralised storage network. Storage miners are rewarded according to their contribution to the network and the mechanics of filecoin secure the network against malicious activity. The objective of this half-day tutorial is to make the audience familiar with IPFS and filecoin and able to use the tools provided by the project for research and development. The tutorial targets both developers and researchers, who may contribute to the project or use it as a tool.