报告题目:A Two-Layer Blockchain Sharding Protocol Leveraging Safety and Liveness for Enhanced Performance

报告时间：2024年7月8日15:00-16:00

报告地点：计算机学院B404会议室

报告人：周永銮

报告人国籍：丹麦

报告人单位：University of Copenhagen

报告人简介：Yongluan Zhou is a professor in the Department of Computer Science (DIKU) at the University of Copenhagen, where he leads the Data Management Systems Lab (DMS Lab). He also heads the MSc in Computer Science at DIKU. Prior to his current position, he worked as an Associate Professor at the University of Southern Denmark (SDU) and as a postdoc at the Ecole Polytechnique Fédérale de Lausanne (EPFL). He earned his Ph.D. in Computer Science from the National University of Singapore (NUS). His research interests span database systems and distributed systems, with his recent focus being on scalable event-driven systems. He has authored more than 80 peer-reviewed research articles in international journals and conference proceedings. He serves on the EDBT Executive Board and the SSDBM Steering Committee and has chaired various international conferences, including DEBS 2022, SSDBM 2022, and EDBT 2020. He has also served on the Program Committees of many other international conferences, including SIGMOD, VLDB, ICDE, EDBT, CIKM, and SSDBM.

报告摘要：Sharding is a critical technique that enhances the scalability of blockchain technology. However, existing protocols often assume adversarial nodes in a general term without considering the different types of attacks, which limits transaction throughput at runtime because attacks on liveness could be mitigated. There have been attempts to increase transaction throughput by separately handling the attacks; however, they have security vulnerabilities. In this talk, I will introduces Reticulum, a novel sharding protocol that overcomes these limitations and achieves enhanced scalability in a blockchain network without security vulnerabilities.

       Reticulum employs a two-phase design that dynamically adjusts transaction throughput based on runtime adversarial attacks on either or both liveness and safety. It consists of ‘control’ and ‘process’ shards in two layers corresponding to the two phases. Process shards are subsets of control shards, with each process shard expected to contain at least one honest node with high confidence. Conversely, control shards are expected to have a majority of honest nodes with high confidence. Reticulum leverages unanimous voting in the first phase to involve fewer nodes in accepting/rejecting a block, allowing more parallel process shards. The control shard finalizes the decision made in the first phase and serves as a lifeline to resolve disputes when they surface. Experiments demonstrate that the unique design of Reticulum empowers high transaction throughput and robustness in the face of different types of attacks in the network, making it superior to existing sharding protocols for blockchain networks.

邀请人：杜博、郑志高