Practical Traceable Receipt-Free Encryption
(2024) 14th International Conference on Security and Cryptography for Networks (SCN 2024) — Location: Amalfi, Italy
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- Abstract
- Traceable Receipt-free Encryption (TREnc) is a verifiable public-key encryption primitive introduced at Asiacrypt 2022. A TREnc allows randomizing ciphertexts in transit in order to remove any subliminal information up to a public trace that ensures the non-malleability of the underlying plaintext. A remarkable property of TREnc is the indistinguishability of the "randomization of chosen ciphertexts" against traceable chosen-ciphertext attacks(TCCA). This property can support applications like voting, and it was shown that receipt-free non-interactive voting, where voters are unable to convince any third party of the content of their vote, can be generically built from a TREnc. While being a very promising primitive, the few existing TREnc mechanisms either require a secret coin CRS or are fairly demanding in time and space requirements. Their security proofs also come with a linear security degradation in the number of challenge ciphertexts. We address these limitations and offer two efficient public coin TREnc mechanisms tailored for the two common tallying approaches in elections: homomorphic and mixnet-based. The TCCA security of our mechanisms also enjoys an almost-tight reduction to SXDH, based on a new randomizable technique of independent interest in the random oracle model. A Rust implementation of our TREnc mechanisms demonstrates that we can verifiably encrypt 64 bits in less than a second, and full group elements in around 30 ms., which is sufficient for most real-world applications. While comparing with other solutions, we show that our approaches lead to the most efficient non-interactive receipt-free voting system to date.
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Devillez, H., Pereira, O., & Peters, T. (2024). Practical Traceable Receipt-Free Encryption. Security and Cryptography for Networks 14th International Conference, SCN 2024, Amalfi (SA), Italy, 2024, Proceedings. Published. 14th International Conference on Security and Cryptography for Networks (SCN 2024), Amalfi, Italy. https://hdl.handle.net/2078.5/216893 (Original work published 2024)