Cryptology ePrint Archive: Report 2020/1373
Transciphering, using FiLIP and TFHE for an efficient delegation of computation
Clément Hoffmann and Pierrick Méaux and Thomas Ricosset
Abstract: Improved filter permutators are designed to build stream ciphers that
can be efficiently evaluated homomorphically. So far the transciphering with
such ciphers has been implemented with homomorphic schemes from the second
generation. In theory the third generation is more adapted for the particular
design of these ciphers. In this article we study how suitable it is in practice. We
implement the transciphering of different instances of the stream cipher family
FiLIP with homomorphic encryption schemes of the third generation using the
TFHE library.
We focus on two kinds of filter for FiLIP. First we consider the direct sum of
monomials, already evaluated using HElib and we show the improvements on
these results. Then we focus on the XOR-threshold filter, we develop strategies
to efficiently evaluate any symmetric Boolean function in an homomorphic way,
allowing us to give the first timings for such filters. We investigate different
approaches for the homomorphic evaluation: using the leveled homomorphic
scheme TGSW, an hybrid approach combining TGSW and TLWE schemes, and
the gate boostrapping approach. We discuss the costs in time and memory and
the impact on delegation of computation of these different approaches, and we
perform a comparison with others transciphering schemes.
Category / Keywords: implementation / Homomorphic Encryption, TFHE, Improved Filter Permutator, Transciphering
Original Publication (in the same form): Indocrypt 2020
Date: received 2 Nov 2020
Contact author: clement hoffmann at uclouvain be, pierrick meaux@uclouvain be, thomas ricosset@thalesgroup com
Available format(s): PDF | BibTeX Citation
Version: 20201102:104635 (All versions of this report)
Short URL: ia.cr/2020/1373
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