Expected-Time Cryptography: Generic Techniques and Applications to Concrete Soundness

Joseph Jaeger and Stefano Tessaro

Abstract

This paper studies concrete security with respect to expected-time adversaries. Our first contribution is a set of generic tools to obtain tight bounds on the advantage of an adversary with expected-time guarantees. We apply these tools to derive bounds in the random-oracle and generic-group models, which we show to be tight. As our second contribution, we use these results to derive concrete bounds on the soundness of public-coin proofs and arguments of knowledge. Under the lens of concrete security, we revisit a paradigm by Bootle at al. (EUROCRYPT '16) that proposes a general Forking Lemma for multi-round protocols which implements a rewinding strategy with expected-time guarantees. We give a tighter analysis, as well as a modular statement. We adopt this to obtain the first quantitative bounds on the soundness of Bulletproofs (Bünz et al., S&P 2018), which we instantiate with our expected-time generic-group analysis to surface inherent dependence between the concrete security and the statement to be proved.

Available format(s)
Category
Foundations
Publication info
A major revision of an IACR publication in TCC 2020
Keywords
concrete securityproof systems
Contact author(s)
jsjaeger @ cs washington edu
History
Short URL
https://ia.cr/2020/1213

CC BY

BibTeX

@misc{cryptoeprint:2020/1213,
author = {Joseph Jaeger and Stefano Tessaro},
title = {Expected-Time Cryptography: Generic Techniques and Applications to Concrete Soundness},
howpublished = {Cryptology ePrint Archive, Paper 2020/1213},
year = {2020},
note = {\url{https://eprint.iacr.org/2020/1213}},
url = {https://eprint.iacr.org/2020/1213}
}

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