Cryptology ePrint Archive: Report 2020/942

RandRunner: Distributed Randomness from Trapdoor VDFs with Strong Uniqueness

Philipp Schindler and Aljosha Judmayer and Markus Hittmeir and Nicholas Stifter and Edgar Weippl

Abstract: Generating randomness collectively has been a long standing problem in distributed computing. It plays a critical role not only in the design of state-of-the-art BFT and blockchain protocols, but also for a range of applications far beyond this field. We present RandRunner, a random beacon protocol with a unique set of guarantees that targets a realistic system model. Our design avoids the necessity of a (Byzantine fault-tolerant) consensus protocol and its accompanying high complexity and communication overhead. We achieve this by introducing a novel extension to verifiable delay functions (VDFs) in the RSA setting that does not require a trusted dealer or distributed key generation (DKG) and only relies on well studied cryptographic assumptions. This design allows RandRunner to tolerate adversarial or failed leaders while guaranteeing safety and liveness of the protocol despite possible periods of asynchrony.

Category / Keywords: cryptographic protocols / distributed randomness, randomness beacon, VDF, RSA

Date: received 31 Jul 2020

Contact author: pschindler at sba-research org

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Version: 20200731:122748 (All versions of this report)

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