Welcome to the resource topic for 2020/730
Title:
On the Security of Time-Lock Puzzles and Timed Commitments
Authors: Jonathan Katz, Julian Loss, Jiayu Xu
Abstract:Time-lock puzzles—problems whose solution requires some amount of sequential effort—have recently received increased interest (e.g., in the context of verifiable delay functions). Most constructions rely on the sequential-squaring conjecture that computing g^{2^T} \bmod N for a uniform g requires at least T (sequential) steps. We study the security of time-lock primitives from two perspectives: - We give the first hardness result about the sequential-squaring conjecture in a non-generic model. Namely, in a quantitative version of the algebraic group model (AGM) that we call the strong AGM, we show that speeding up sequential squaring is as hard as factoring N. - We then focus on timed commitments, one of the most important primitives that can be obtained from time-lock puzzles. We extend existing security definitions to settings that may arise when using timed commitments in higher-level protocols, and give the first construction of non-malleable timed commitments. As a building block of independent interest, we also define (and give constructions for) a related primitive called timed public-key encryption.
ePrint: https://eprint.iacr.org/2020/730
Talk: https://www.youtube.com/watch?v=aPccI3CNNYU
Slides: https://iacr.org/submit/files/slides/2020/tcc/tcc2020/223/slides.pptx
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