Prism: Scaling Blockchain Consensus to Its Physical Limits

Abstract

Blockchains were designed by Satoshi Nakamoto to maintain a distributed ledger. In addition to security, important performance measures of a blockchain protocol are its transaction throughput and confirmation latency. For example, Bitcoin has a throughput of about 3-7 transactions per second, and confirmation latencies on the order of hours. In a decentralized setting, these measures are limited by two underlying physical network attributes: communication capacity and speed-of-light propagation delay. In this work we introduce Prism, a new proof-of-work blockchain protocol that can achieve 1) security against up to 50% adversarial hash power; 2) optimal throughput up to the capacity C of the network; 3) confirmation latency for honest transactions proportional to the propagation delay D, with confirmation error probability exponentially small in the bandwidth-delay product CD; 4) eventual total ordering of all transactions. We demonstrate Prism’s performance on an implementation that achieves a throughput of over 70,000 transactions per second and a confirmation latency of tens of seconds on networks of up to 1,000 EC2 virtual machines.

Biography

Giulia Fanti is an Assistant Professor of Electrical and Computer Engineering at Carnegie Mellon University. Her research interests span the algorithmic foundations of blockchains, distributed systems, privacy-preserving technologies, and machine learning. She is a fellow for the World Economic Forum’s Global Future Council on Cybersecurity, and has received best paper awards from ACM Sigmetrics and ACM MobiHoc, as well as an NSF Graduate Research Fellowship. She obtained her Ph.D. in EECS from U.C. Berkeley and her B.S. in ECE from Olin College of Engineering.