Speaker: Ittay Eyal (Cornell)
Title: Challenges in Blockchain Protocols
Abstract:
The study of security in decentralized large-scale distributed systems has made a large leap forward with the introduction of Blockchain-based cyber-currencies, starting with Bitcoin.
This talk will discuss three results tackling central challenges that were exposed by this progress.
Cyber-currencies, as the name implies, implement secure and reliable digital currencies, but their promise has grown beyond currency, for example to so-called smart contracts and to digital asset infrastructure.
This is mainly due to the introduction of Bitcoin's blockchain protocol, which achieves a variant of consensus using proof-of-work: participants solve computationally-difficult puzzles, send a proof, and are compensated for their efforts.
I'll show that the bound on the resilience of blockchain protocols is significantly worse than previously thought. This is due to the selfish mining attack, which is effective against all blockchain protocols known to date. Next, I'll show that security does not stand at odds with performance at the adversarial environments where blochchain algorithms live. I'll present a novel blockchain protocol that achieves both security and optimal performance, demonstrated in the largest blockchain lab-experiment to date. Finally, I'll address an issue that is general to the proof-of-work incentive mechanism, namely that participants tend to form coalitions, leading to centralization. I'll present a game-theoretic analysis of a novel attack among such coalitions, which leads to surprising consequences.