Efficient Identity-Based Encryption with Tight Adaptive Anonymity from RLWE

In this paper, we propose an efficient identity-based encryption (IBE) scheme based on the ring learning with errors (RLWE) assumption in the (quantum) random oracle model. Our IBE scheme is (asymptotically) as efficient as the most practical lattice-based IBE scheme proposed by Ducal et al. (ASIACRYPT 2014). Furthermore, our scheme is adaptively and anonymously secure, and its security reduction is tight. We design our IBE scheme by instantiating the framework of Gentry et al. (STOC 2008) using the compact preimage sampling proposed by Yu et al. (CRYPTO 2023). The tightness of our IBE scheme is obtained by combining the proof technique of Katsumata et al. (ASIACRYPT 2018) with the results for ideal lattices developed by Mera et al. (PKC 2022).