Cryptology ePrint Archive: Report 2021/634

Setting Up Efficient TFHE Parameters for Multivalue Plaintexts and Multiple Additions

Jakub Klemsa

Abstract: Unlike traditional and/or standardized ciphers, TFHE offers much space for the setup of its parameters. Not only the parameter choice affects the plaintext space size and security, it also greatly impacts the performance of TFHE, in particular, its bootstrapping. In this paper, we provide an exhaustive description of TFHE, including its foundations, (functional) bootstrapping and error propagation during all operations. In addition, we outline a bootstrapping scenario without the key switching step. Based on our thorough summary, we suggest an approach for the setup of TFHE parameters with particular respect to bootstrapping efficiency. Finally, we propose twelve setups of real-world TFHE parameters for six different scenarios with and without key switching, respectively, and we compare their performance. N.b.: This is a technical paper, which is mainly intended for researchers interested in TFHE. However, due to its self-containment, it shall be accessible also for readers with a basic knowledge of TFHE.

Category / Keywords: fully homomorphic encryption, TFHE

Date: received 13 May 2021, last revised 2 Jul 2021

Contact author: klemsjak at fel cvut cz

Available format(s): PDF | BibTeX Citation

Note: updated parameter set C according to intended application

Version: 20210702:135620 (All versions of this report)

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