Paper 2021/100

SPURT: Scalable Distributed Randomness Beacon with Transparent Setup

Sourav Das and Vinith Krishnan and Irene Miriam Isaac and Ling Ren

Abstract

Having shared access to high-quality random numbers is essential in many important applications. Yet, existing constructions of distributed random beacons still have limitations such as imperfect security guarantees, strong setup or network assumptions, or high costs. In this paper, we present SPURT, an efficient distributed randomness beacon protocol that does not require any trusted or expensive setup and is secure against a malicious adversary that controls up to one-third of the nodes in a partially synchronous network. We formally prove that each output of SPURT is unpredictable, bias-resistant, and publicly verifiable. SPURT has an amortized total communication cost of O(\lambda n^2) per beacon output in the fault-free case and O(\lambda n^2\log n + n^3) in the worst case. We implement SPURT and evaluate it using a network of up to 128 nodes running in geographically distributed AWS instances. Our evaluation shows that SPURT has practical computation and bandwidth costs and can produce beacon outputs every second for a network of 64 nodes, and every 3 seconds for a network of 128 nodes.

Note: New PVSS scheme assuming DBDH and new experimental results.