Systems Research Group

Abstract:

Safety and liveness are the two classical security properties of consensus protocols that are used in blockchains and other systems. Recent works have strengthened safety with accountability: should any safety violation occur, then “many” adversary nodes can be proven to be protocol violators. In this talk, we explore if and how analogous accountability guarantees are achievable for liveness. We prove a precise characterization: accountable liveness is achievable if and only if more nodes are honest than adversarial, and “the network is more synchronous than asynchronous” (made precise in the talk). What is more, our protocol identifies a near-optimal number of adversarial nodes following a liveness violation. Our results provide rigorous foundations for liveness-accountability heuristics such as the “inactivity leaks” employed in Ethereum.

Bio:

Joachim Neu is a post-doc Research Partner at a16z Crypto Research led by Tim Roughgarden. Previously, Joachim earned a PhD from Stanford, advised by David Tse. His current research focus is blockchain-era consensus and decentralized-systems security. His broader interests include distributed computing and systems, applied cryptography, and networking and communications.