Post-quantum Privacy for Traceable Receipt-Free Encryption
(2026) IACR International Conference on Public-Key Cryptography — Location: West Palm Beach, FL, USA (25.May.2026)
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- Abstract
- Traceable Receipt-free Encryption (TREnc) has recently been introduced by Devillez, Pereira and Peters (Asiacrypt'22) as a verifiable public-key encryption primitive allowing to randomize ciphertexts 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 harvest 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.
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Citations
De Perthuis, P., & Peters, T. (2026). Post-quantum Privacy for Traceable Receipt-Free Encryption. Public-Key Cryptography – PKC 2026, 16554, XVI, 528. https://doi.org/10.1007/978-3-032-26740-5_3 (Original work published 2026)