Paper 2022/447

Leveled Multikey FHE with constant-size ciphertexts from RLWE

Vanesa Daza and Paz Morillo and Sergi Rovira

Abstract

A multi-key fully homomorphic encryption (MKFHE) scheme allows a public server to evaluate arbitrary circuits over ciphertexts encrypted under different keys. One of the main drawbacks of MKFHE schemes is the need for a ciphertext expansion procedure prior to evaluation, which combines ciphertexts encrypted under different keys to a (much larger) ciphertext encrypted under a concatenated key. In this paper, we present a new (leveled) RLWE-based MKFHE scheme without ciphertext expansion.