{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T22:34:20Z","timestamp":1775774060783,"version":"3.50.1"},"reference-count":44,"publisher":"International Association for Cryptologic Research","license":[{"start":{"date-parts":[[2024,1,8]],"date-time":"2024-01-08T00:00:00Z","timestamp":1704672000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IACR CiC"],"accepted":{"date-parts":[[2024,3,5]]},"abstract":" Fully Homomorphic Encryption (FHE) is a powerful tool to achieve non-interactive privacy preserving protocols with optimal computation\/communication complexity. However, the main disadvantage is that the actual communication cost (bandwidth) is high due to the large size of FHE ciphertexts. As a solution, a technique called transciphering (also known as Hybrid Homomorphic Encryption) was introduced to achieve almost optimal bandwidth for such protocols. However, all existing works require clients to fix a precision for the messages or a mathematical structure for the message space beforehand. It results in unwanted constraints on the plaintext size or underlying structure of FHE based applications.<\/jats:p>\n In this article, we introduce a new approach for transciphering which does not require fixed message precision decided by the client, for the first time. In more detail, a client uses any kind of FHE-friendly symmetric cipher for \n \n {<\/mml:mo>\n 0<\/mml:mn>\n ,<\/mml:mo>\n 1<\/mml:mn>\n }<\/mml:mo>\n <\/mml:mrow>\n <\/mml:math> to send its input data encrypted bit-by-bit, then the server can choose a precision \n \n p<\/mml:mi>\n <\/mml:mrow>\n <\/mml:math> depending on the application and homomorphically transforms the encrypted bits into FHE ciphertexts encrypting integers in \n \n \n \u2124<\/mml:mi>\n p<\/mml:mi>\n <\/mml:msub>\n <\/mml:mrow>\n <\/mml:math>. To illustrate our new technique, we evaluate a transciphering using FiLIP cipher and adapt the most practical homomorphic evaluation technique [CCS'22] to keep the practical latency. As a result, our proof-of-concept implementation for \n \n p<\/mml:mi>\n <\/mml:mrow>\n <\/mml:math> from \n \n \n 2<\/mml:mn>\n 2<\/mml:mn>\n <\/mml:msup>\n <\/mml:mrow>\n <\/mml:math> to \n \n \n 2<\/mml:mn>\n 8<\/mml:mn>\n <\/mml:msup>\n <\/mml:mrow>\n <\/mml:math> takes only from \n \n 13<\/mml:mn>\n <\/mml:mrow>\n <\/mml:math> ms to \n \n 137<\/mml:mn>\n <\/mml:mrow>\n <\/mml:math> ms. <\/jats:p>","DOI":"10.62056\/anxrxrxqi","type":"journal-article","created":{"date-parts":[[2024,4,9]],"date-time":"2024-04-09T19:27:10Z","timestamp":1712690830000},"update-policy":"https:\/\/doi.org\/10.62056\/adfjwm02dj","source":"Crossref","is-referenced-by-count":9,"title":["Towards Practical Transciphering for FHE with Setup Independent of the Plaintext Space"],"prefix":"10.62056","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5733-4341","authenticated-orcid":false,"given":"Pierrick","family":"M\u00e9aux","sequence":"first","affiliation":[{"name":"University of Luxembourg","place":["Esch sur Alzette, Luxembourg"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0557-3540","authenticated-orcid":false,"given":"Jeongeun","family":"Park","sequence":"additional","affiliation":[{"name":"Norwegian University of Science and Technology (NTNU)","place":["Trondheim, Norway"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1303-3760","authenticated-orcid":false,"given":"Hilder","family":"Pereira","sequence":"additional","affiliation":[{"name":"University of Campinas (UNICAMP)","place":["Campinas, Brazil"]}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"48349","published-online":{"date-parts":[[2024,4,9]]},"reference":[{"key":"ref1:tueno2020non","doi-asserted-by":"publisher","first-page":"174","DOI":"10.1007\/978-3-030-49669-2_10","article-title":"Non-interactive private decision tree evaluation","volume-title":"IFIP Annual Conference on Data and Applications Security and\n Privacy","author":"Anselme Tueno","year":"2020"},{"key":"ref2:PoPets:JubSir21","doi-asserted-by":"publisher","first-page":"111","DOI":"10.2478\/popets-2021-0020","article-title":"Efficient homomorphic evaluation of k-NN classifiers","volume":"2021","author":"Martin Zuber","year":"2021","journal-title":"Proceedings on Privacy Enhancing Technologies"},{"key":"ref3:SortingHat","series-title":"CCS '22","isbn-type":"print","doi-asserted-by":"publisher","first-page":"563","DOI":"10.1145\/3548606.3560702","article-title":"SortingHat: Efficient Private Decision Tree Evaluation via\n Homomorphic Encryption and Transciphering","volume-title":"Proceedings of the 2022 ACM SIGSAC Conference on Computer\n and Communications Security","author":"Kelong Cong","year":"2022","ISBN":"https:\/\/id.crossref.org\/isbn\/9781450394505"},{"key":"ref4:MELECON:BraPeiMea22","doi-asserted-by":"publisher","first-page":"18","DOI":"10.1109\/MELECON53508.2022.9843009","article-title":"Homomorphic Encryption for Privacy-Friendly Augmented\n Democracy","volume-title":"2022 IEEE 21st Mediterranean Electrotechnical Conference\n (MELECON)","author":"Matthieu Brabant","year":"2022"},{"key":"ref5:Nature:KJLIS22","doi-asserted-by":"publisher","DOI":"10.1038\/s41467-022-32168-5","article-title":"Secure human action recognition by encrypted neural network\n inference","volume":"13","author":"Miran Kim","year":"2022","journal-title":"Nature Communications"},{"key":"ref6:ZAMANN","article-title":"Deep Neural Networks for Encrypted Inference with TFHE","author":"Andrei Stoian","year":"2023"},{"key":"ref7:CCS:CheChiRen19","doi-asserted-by":"publisher","first-page":"345","DOI":"10.1145\/3319535.3354226","article-title":"Onion Ring ORAM: Efficient Constant Bandwidth Oblivious\n RAM from (Leveled) TFHE","volume-title":"ACM CCS 2019: 26th Conference on Computer and Communications\n Security","author":"Hao Chen","year":"2019"},{"key":"ref8:Panacea","article-title":"Panacea: Non-interactive and Stateless Oblivious RAM","author":"Kelong Cong","year":"2023"},{"key":"ref9:JC:CGGI20","doi-asserted-by":"publisher","first-page":"34","DOI":"10.1007\/s00145-019-09319-x","article-title":"TFHE: Fast Fully Homomorphic Encryption Over the Torus","volume":"33","author":"Ilaria Chillotti","year":"2020","journal-title":"Journal of Cryptology"},{"key":"ref10:CCSW:NaeLauVai11","doi-asserted-by":"publisher","first-page":"113","DOI":"10.1145\/2046660.2046682","article-title":"Can homomorphic encryption be practical?","volume-title":"Proceedings of the 3rd ACM Cloud Computing Security\n Workshop, CCSW 2011, Chicago, IL, USA, October 21, 2011","author":"Michael Naehrig","year":"2011"},{"key":"ref11:EC:ARSTZ15","series-title":"Lecture Notes in Computer Science","doi-asserted-by":"publisher","first-page":"430","DOI":"10.1007\/978-3-662-46800-5_17","article-title":"Ciphers for MPC and FHE","volume-title":"Advances in Cryptology \u2013 EUROCRYPT\u00a02015, Part\u00a0I","volume":"9056","author":"Martin R. 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