Paper 2024/2087

Post-Quantum Privacy for Traceable Receipt-Free Encryption

Paola de Perthuis, Centrum Wiskunde & Informatica
Thomas Peters, Université catholique de Louvain
Abstract

Traceable Receipt-free Encryption (TREnc) has recently been introduced (Asiacrypt’22) as a verifiable public-key encryption primitive allowing to randomize ciphertexts in transit in order to remove any subliminal information up to a public trace which prevents the malleability of the underlying plaintexts. This unique feature generically enables the construction of voting systems by allowing voters to encrypt their votes, tracing whether a published ballot takes their choices into account, and preventing them from proving how they voted. While being a very promising primitive, the few existing TREnc mechanisms solely rely on discrete-logarithm related assumptions making them vulnerable to the well-known record-now/decrypt-later attack in the wait of quantum computers. In this article, we address this limitation by building the first TREnc which can be safely used today until the advent of quantum adversaries. More precisely, based on the observation that security must hold at the time the primitive is used while only privacy should withstand in the post-quantum era, our solution relies on a mix of pre-quantum and post-quantum cryptography. As a first contribution, we generalize the original TREnc primitive that is too restrictive to be easily compatible with built-in lattice-based semantically-secure encryption. Our more flexible model keeps all the ingredients generically implying receipt-free voting. Next, we design our construction with the following essential properties for trustworthy elections: (i) it is provably-secure in the standard model; (ii) it relies on standard assumptions, namely Ring Learning With Errors (RLWE) coupled with pairing-based statistical zero-knowledge simulation-sound SXDH-based proofs; and (iii) it further enjoys a public-coin common reference string removing the need of a trusted setup.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint.
Keywords
TraceabilityVoting SystemRandomizable EncryptionRandomizable ProofsTCCAPost-QuantumLattice-Based
Contact author(s)
Paola de Perthuis @ cwi nl
thomas peters @ uclouvain be
History
2025-05-17: last of 2 revisions
2024-12-27: received
See all versions
Short URL
https://ia.cr/2024/2087
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2024/2087,
      author = {Paola de Perthuis and Thomas Peters},
      title = {Post-Quantum Privacy for Traceable Receipt-Free Encryption},
      howpublished = {Cryptology {ePrint} Archive, Paper 2024/2087},
      year = {2024},
      url = {https://eprint.iacr.org/2024/2087}
}
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