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Paper 2024/1162

Practical Traceable Receipt-Free Encryption

Henri Devillez, UCLouvain
Olivier Pereira, UCLouvain, Microsoft Research
Thomas Peters, UCLouvain
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.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Published elsewhere. Major revision. SCN 2024
Keywords
Receipt-freenesstightnessvoting
Contact author(s)
henri devillez @ uclouvain be
olivier pereira @ uclouvain be
thomas peters @ uclouvain be
History
2024-07-19: approved
2024-07-17: received
See all versions
Short URL
https://ia.cr/2024/1162
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2024/1162,
      author = {Henri Devillez and Olivier Pereira and Thomas Peters},
      title = {Practical Traceable Receipt-Free Encryption},
      howpublished = {Cryptology {ePrint} Archive, Paper 2024/1162},
      year = {2024},
      url = {https://eprint.iacr.org/2024/1162}
}
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