Paper 2021/1423

Encryption to the Future: A Paradigm for Sending Secret Messages to Future (Anonymous) Committees

Matteo Campanelli, Bernardo David, Hamidreza Khoshakhlagh, Anders Konring, and Jesper Buus Nielsen

Abstract

A number of recent works have constructed cryptographic protocols with flavors of adaptive security by having a randomly-chosen anonymous committee run at each round. Since most of these protocols are stateful, transferring secret states from past committees to future, but still unknown, committees is a crucial challenge. Previous works have tackled this problem with approaches tailor-made for their specific setting, which mostly rely on using a blockchain to orchestrate auxiliary committees that aid in state hand-over process. In this work, we look at this challenge as an important problem on its own and initiate the study of Encryption to the Future (EtF) as a cryptographic primitive. First, we define a notion of a \emph{non-interactive} EtF scheme where time is determined with respect to an underlying blockchain and a lottery selects parties to receive a secret message at some point in the future. While this notion seems overly restrictive, we establish two important facts: 1. if used to encrypt towards parties selected in the ``far future'', EtF implies witness encryption for NP over a blockchain; 2. if used to encrypt only towards parties selected in the ``near future'', EtF is not only sufficient for transferring state among committees as required by previous works, but also captures previous tailor-made solutions. To corroborate these results, we provide a novel construction of EtF based on witness encryption over commitments (cWE), which we instantiate from a number of standard assumptions via a construction based on generic cryptographic primitives. Finally, we show how to use ``near future'' EtF to obtain ``far future'' EtF with a protocol based on an auxiliary committee whose communication complexity is \emph{independent} of the length of plaintext messages being sent to the future.

Metadata
Available format(s)
PDF
Category
Cryptographic protocols
Publication info
Preprint. Minor revision.
Keywords
applicationsblockchainwitness encryptionYOSO
Contact author(s)
matteo @ protocol ai
jbn @ au dk
beda @ itu dk
hamidreza @ cs au dk
konr @ itu dk
History
2022-02-24: last of 3 revisions
2021-10-24: received
See all versions
Short URL
https://ia.cr/2021/1423
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2021/1423,
      author = {Matteo Campanelli and Bernardo David and Hamidreza Khoshakhlagh and Anders Konring and Jesper Buus Nielsen},
      title = {Encryption to the Future: A Paradigm for Sending Secret Messages to Future (Anonymous) Committees},
      howpublished = {Cryptology ePrint Archive, Paper 2021/1423},
      year = {2021},
      note = {\url{https://eprint.iacr.org/2021/1423}},
      url = {https://eprint.iacr.org/2021/1423}
}
Note: In order to protect the privacy of readers, eprint.iacr.org does not use cookies or embedded third party content.