■ 연사: 박정은 박사 (KU LEUVEN, COSIC)

■ 제목: FHE based on NTRU: challenges and solutions

■ 일시: 2023년 7월 18일 (화) 17:00

■ 장소: 종합과학관 A동 317호

■ 초록: The NTRU problem is a promising candidate to build efficient Fully Homomorphic Encryption (FHE). However, all the existing proposals (e.g. LTV, YASHE) need so-called `overstretched' parameters of NTRU to enable homomorphic operations. It was shown by Albrecht et al. (CRYPTO 2016) that these parameters are vulnerable against subfield lattice attacks.

Based on a recent, more detailed analysis of the overstretched NTRU assumption by Ducas and van Woerden (ASIACRYPT 2021), we construct two FHE schemes whose NTRU parameters lie outside the overstretched range. 

     In this talk, we will discuss about possible advantages and challenges of constructing FHE over NTRU, about the problems that the previous NTRU-based schemes had, and finally, we will show how two new schemes i) based solely on NTRU and ii) combining LWE with NTRU to obtain a bootstrapping that is faster than TFHE's bootstrapping and uses shorter keys.

    The first scheme is based solely on NTRU and demonstrates competitive performance against the state-of-the-art FHE schemes including TFHE. Our second scheme, which is based on both the NTRU and LWE assumptions, outperforms TFHE with a 28% faster bootstrapping and 45% smaller bootstrapping and key-switching keys.

■ 문의: (02)3277-6990/ims@ewha.ac.kr