CryptoDB
Black-Box Timed Commitments from Time-Lock Puzzles
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| Conference: | TCC 2024 |
| Abstract: | A Timed Commitment (TC) with time parameter $t$ is hiding for time at most $t$, that is, commitments can be force-opened by any third party within time $t$. In addition to various cryptographic assumptions, the security of all known TC schemes relies on the sequentiality assumption of repeated squarings in hidden-order groups. The repeated squaring assumption is therefore a security bottleneck. In this work, we give a black-box construction of TCs from any time-lock puzzle (TLP) by additionally relying on one-way permutations and collision-resistant hashing. Currently, TLPs are known from (a) the specific repeated squaring assumption, (b) the general (necessary) assumption on the \emph{existence of worst-case non-parallelizing languages} and indistinguishability obfuscation, and (c) any iteratively sequential function and the hardness of the circular small-secret LWE problem. The latter admits a plausibly post-quantum secure instantiation. Hence, thanks to the generality of our transform, we get i) the first TC whose \emph{timed} security is based on the the existence of non-parallelizing languages and ii) the first TC that is plausibly post-quantum secure. We first define \emph{quasi publicly-verifiable} TLPs (QPV-TLPs) and construct them from any standard TLP in a black-box manner without relying on any additional assumptions. Then, we devise a black-box commit-and-prove system to transform any QPV-TLPs into a TC. |
BibTeX
@inproceedings{tcc-2024-34730,
title={Black-Box Timed Commitments from Time-Lock Puzzles},
publisher={Springer-Verlag},
author={Hamza Abusalah and Gennaro Avitabile},
year=2024
}