CryptoDB
Non-Malleable Time-Lock Puzzles and Applications
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| Abstract: | Time-lock puzzles are a mechanism for sending messages "to the future", by allowing a sender to quickly generate a puzzle with an underlying message that remains hidden until a receiver spends a moderately large amount of time solving it. We introduce and construct a variant of a time-lock puzzle which is non-malleable, which roughly guarantees that it is impossible to "maul" a puzzle into one for a related message without solving it. Using non-malleable time-lock puzzles, we achieve the following applications: - The first fair non-interactive multi-party protocols for coin flipping and auctions in the plain model without setup. - Practically efficient fair multi-party protocols for coin flipping and auctions proven secure in the (auxiliary-input) random oracle model. As a key step towards proving the security of our protocols, we introduce the notion of functional non-malleability, which protects against tampering attacks that affect a specific function of the related messages. To support an unbounded number of participants in our protocols, our time-lock puzzles satisfy functional non-malleability in the fully concurrent setting. We additionally show that standard (non-functional) non-malleability is impossible to achieve in the concurrent setting (even in the random oracle model). |
Video from TCC 2021
BibTeX
@article{tcc-2021-31539,
title={Non-Malleable Time-Lock Puzzles and Applications},
booktitle={Theory of Cryptography;19th International Conference},
publisher={Springer},
doi={10.1007/978-3-030-90456-2_15},
author={Cody Freitag and Ilan Komargodski and Rafael Pass and Naomi Sirkin},
year=2021
}