Continuous verifiable delay functions

Naomi Ephraim*, Cody Freitag, Ilan Komargodski, Rafael Pass

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

23 Scopus citations

Abstract

We introduce the notion of a continuous verifiable delay function (cVDF): a function g which is (a) iteratively sequential—meaning that evaluating the iteration g(t) of g (on a random input) takes time roughly t times the time to evaluate g, even with many parallel processors, and (b) (iteratively) verifiable—the output of g(t) can be efficiently verified (in time that is essentially independent of t). In other words, the iterated function g(t) is a verifiable delay function (VDF) (Boneh et al., CRYPTO ’18), having the property that intermediate steps of the computation (i.e., g (t') for t'< t) are publicly and continuously verifiable. We demonstrate that cVDFs have intriguing applications: (a) they can be used to construct public randomness beacon that only require an initial random seed (and no further unpredictable sources of randomness), (b) enable outsourceable where any part of the VDF computation can be verifiably outsourced, and (c) have deep complexity-theoretic consequences: in particular, they imply the existence of depth-robust moderately-hard Nash equilibrium problem instances, i.e. instances that can be solved in polynomial time yet require a high sequential running time. Our main result is the construction of a cVDF based on the repeated squaring assumption and the soundness of the Fiat-Shamir (FS) heuristic for constant-round proofs. We highlight that when viewed as a (plain) VDF, our construction requires a weaker FS assumption than previous ones (earlier constructions require the FS heuristic for either super-logarithmic round proofs, or for arguments).

Original languageAmerican English
Title of host publicationAdvances in Cryptology – EUROCRYPT 2020 - 39th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Proceedings
EditorsAnne Canteaut, Yuval Ishai
PublisherSpringer
Pages125-154
Number of pages30
ISBN (Print)9783030457266
DOIs
StatePublished - 2020
Externally publishedYes
Event39th Annual International Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2020 - Zagreb, Croatia
Duration: 10 May 202014 May 2020

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume12107 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference39th Annual International Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2020
Country/TerritoryCroatia
CityZagreb
Period10/05/2014/05/20

Bibliographical note

Publisher Copyright:
© International Association for Cryptologic Research 2020.

Fingerprint

Dive into the research topics of 'Continuous verifiable delay functions'. Together they form a unique fingerprint.

Cite this