NC-Max: Breaking the Security-Performance Tradeoff in Nakamoto Consensus
报告地点：第一馆408，腾讯会议532 905 353
First implemented in Bitcoin, Nakamoto Consensus (NC) is the most influential consensus protocol in cryptocurrencies despite all the alternative protocols designed afterward. Nevertheless, NC is trapped by a security-performance tradeoff. While existing efforts mostly attempt to break this tradeoff via abandoning or adjusting NC's backbone protocol, we alternatively forward the relevance of the network layer. We identify and experimentally prove that the crux resides with the prolonged block propagation latency caused by not-yet-propagated transactions---fresh transactions. We thus present a two-step mechanism to eliminate fresh transactions and therefore remove the limits upon NC's performance imposed by its security demands, realizing NC's untapped potential to its maximum. Further, we introduce an accurate dynamic difficulty adjustment mechanism (DAM) to explore the real-time network condition and to adjust the protocol's throughput accordingly. Implementing the two-step mechanism and the DAM, we propose NC-Max, whose (1) security is analyzed, proving that it provides stronger resistance than NC against selfish mining and transaction withholding attacks, and (2) performance is evaluated, showing that it exhausts the full throughput supported by the network, and shortens the transaction confirmation latency by at least a factor of four compared to NC without compromising security.
Dr. Ren Zhang is a researcher at Nervos and Cryptape Co., Ltd., working on the exciting field of cryptocurrencies and blockchains. He is best known for his work on attacking Bitcoin Unlimited and other blockchain consensus protocols. His research interests also include P2P network security and cryptography. He has a B.S. in math and an M.S. in computer science, both from Peking University, China. He received his Ph.D. in 2019 from the COSIC research group, KU Leuven, Belgium, supervised by professor Bart Preneel. During his Ph.D., he interned at Blockstream, supervised by Bitcoin core developers Pieter Wuille and Gregory Maxwell. He enjoys solving challenging problems and participating in competitions, among which he won the first place in the professional category of 2014 International Olympiad in Cryptography (NSUCRYPTO). Ren is a receiver of 2019 "Outstanding Self-Financed Student Studying Abroad Award" issued by the China Scholarship Council. Ren is a PC member of FC'21 and NDSS'21.