Paper 2023/1024

Timed Secret Sharing

Alireza Kavousi, University College London
Aydin Abadi, University College London
Philipp Jovanovic, University College London

Secret sharing has been a promising tool in cryptographic schemes for decades. It allows a dealer to split a secret into some pieces of shares that carry no sensitive information on their own when being treated individually but lead to the original secret when having a sufficient number of them together. Existing schemes lack considering a guaranteed delay prior to secret reconstruction and implicitly assume once the dealer shares the secret, a sufficient number of shareholders will get together and recover the secret at their wish. This, however, may lead to security breaches when a timely reconstruction of the secret matters as the early knowledge of a single revealed share is catastrophic assuming a threshold adversary. This paper presents the notion of timed secret sharing (TSS), providing lower and upper time bounds for secret reconstruction with the use of time-based cryptography. The recent advances in the literature including short-lived proofs [Asiacrypt 2022], enable us to realize an upper time bound shown to be useful in breaking public goods game, an inherent issue in secret sharing-based systems. Moreover, we establish an interesting trade-off between time and fault tolerance in a secret sharing scheme by having dealer gradually release additional shares over time, offering another approach with the same goal. We propose several constructions that offer a range of security properties while maintaining practical efficiency. Our constructions leverage a variety of techniques and state-of-the-art primitives.

Available format(s)
Cryptographic protocols
Publication info
Secret sharingtime-based cryptographyverifiable delay functiontime-lock puzzle
Contact author(s)
alireza kavousi 21 @ ucl ac uk
aydin abadi @ ucl ac uk
p jovanovic @ ucl ac uk
2023-07-03: approved
2023-07-02: received
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      author = {Alireza Kavousi and Aydin Abadi and Philipp Jovanovic},
      title = {Timed Secret Sharing},
      howpublished = {Cryptology ePrint Archive, Paper 2023/1024},
      year = {2023},
      note = {\url{}},
      url = {}
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