Alysson Bessani, LASIGE’s integrated member, won the best paper award at the 40th International Symposium on Reliable Distributed Systems (SRDS 2021), co-authored with Hans P. Reiser and Christian Berger.

The paper “Making Reads in BFT State Machine Replication Fast, Linearizable, and Live” identified a 20-year-old dormant bug on MIT’s Practical Byzantine Fault Tolerance (PBFT) – the most important Byzantine Fault Tolerant State Machine Replication/Consensus – which is used in several permissioned blockchains and showed that the consensus-free read optimization proposed in PBFT may lead liveness problems. Given PBFT’s broad influence, its design and optimizations influenced many BFT protocols and systems that followed, e.g., BFT-SMaRt.

Notably, the problem affects not only the optimized read-only operations but also standard, totally-ordered operations. The researchers showed this weakness by presenting an attack in which a malicious leader blocks correct clients and presented two solutions for patching the protocol, making read-only operations fast and correct. The two solutions were implemented on BFT-SMaRt and evaluated in different scenarios, showing their effectiveness in preventing the identified attack.

The preprint can be found here

SRDS 2021 is a forum for researchers and practitioners interested in distributed systems design, development, and evaluation, with an emphasis on reliability, availability, safety, dependability, security, verification, and real-time systems. It was held virtually in September, 20- 23, 2021.