Paper 2022/1718

Identity-based Matchmaking Encryption with Stronger Security and Instantiation on Lattices

Abstract

An identity-based matchmaking encryption (IB-ME) scheme proposed at JOC 2021 supports anonymous but authenticated communications in a way that communication parties can both specify the senders or receivers on the fly. IB-ME is easy to be used in several network applications requiring privacy-preserving for its efficient implementation and special syntax. In the literature, IB-ME schemes are built from the variants of Diffie-Hellman assumption and all fail to retain security for quantum attackers. Despite the rigorous security proofs in previous security models, the existing schemes are still possibly vulnerable to some potential neglected attacks. Aiming at the above problems, we provide a stronger security definition of authenticity considering new attacks to fit real-world scenarios and then propose a generic construction of IB-ME satisfying the new model. Inspired by the prior IB-ME construction of Chen et al., the proposed scheme is constructed by combining 2-level anonymous hierarchical IBE (HIBE) and identity-based signature (IBS) schemes. In order to upgrade lattice-based IB-ME with better efficiency, we additionally improve a lattice IBS, as an independent technical contribution, to shorten its signature and thus reduce the final IB-ME ciphertext size. By combining the improved IBS and any 2-level adaptively-secure lattice-based HIBE with anonymity, we finally obtain the first lattice-based construction that implements IB-ME directly.