When using FHE in the setting with multiple parties, a major consideration is key management. There are two main paths, either each party keeps their own key, called multikey FHE (MKFHE), or the parties use some key agreement procedure, often MPC, to agree on some common key, which can then be used as if this were the single key setting, called multiparty FHE (MPFHE). The first such work was based on the NTRU problem, which brought with it some major benefits in both efficiency and key size. It was later found to be insecure due to using overstretched parameters, after which nearly all work in FHE for all settings has been based on LWE.
Recently, NTRU-based FHE has made a return due to FINAL. In this work, we expand FINAL to both the MKFHE and MPFHE settings, bringing the efficiency and key size benefits of NTRU to multiple parties, without using overstretched parameters.
About the speaker
Oliver is a PhD Candidate at COSIC, KU Leuven. After completing his Master’s in Mathematics at KU Leuven, he’s published works on FHE, Garbled Circuits, and Secret Sharing-based MPC.
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