Online Payments by Merely Broadcasting Messages

• Published in: 2020 50th Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN) pp. 26 - 38
• Main Authors: Collins, Daniel, Guerraoui, Rachid, Komatovic, Jovan, Kuznetsov, Petr, Monti, Matteo, Pavlovic, Matej, Pignolet, Yvonne-Anne, Seredinschi, Dragos-Adrian, Tonkikh, Andrei, Xygkis, Athanasios
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2020
• Subjects: asynchronous; Bitcoin; Broadcasting; byzantine reliable broadcast; consensus; consensus free; Contracts; deterministic; efficient; online payments; Protocols; Robustness; Throughput
• DOI: 10.1109/DSN48063.2020.00023

We address the problem of online payments, where users can transfer funds among themselves. We introduce Astro, a system solving this problem efficiently in a decentralized, deterministic, and completely asynchronous manner. Astro builds on the insight that consensus is unnecessary to prevent double-spending. Instead of consensus, Astro relies on a weaker primitive---Byzantine reliable broadcast---enabling a simpler and more efficient implementation than consensus-based payment systems. In terms of efficiency, Astro executes a payment by merely broadcasting a message. The distinguishing feature of Astro is that it can maintain performance robustly, i.e., remain unaffected by a fraction of replicas being compromised or slowed down by an adversary. Our experiments on a public cloud network show that Astro can achieve near-linear scalability in a sharded setup, going from 10K payments/sec (2 shards) to 20K payments/sec (4 shards). In a nutshell, Astro can match VISA-level average payment throughput, and achieves a 5× improvement over a state-of-the-art consensus-based solution, while exhibiting sub-second 95^th percentile latency.