Paper 2023/444

Compact Bounded-Collusion Identity-based Encryption via Group Testing

Abstract

Bounded-collusion identity-based encryption (BC-IBE) is a variant of identity-based encryption, where an adversary obtains user secrete keys corresponding to at most $d$ identities. From results of existing work, it is proven that BC-IBE can be constructed from public key encryption (PKE) with several properties. In particular, we focus on post-quantum PKE schemes submitted to the NIST PQC competition, as the underlying PKE of BC-IBE schemes. This is because post-quantum cryptography is one of active research areas, due to recent advancement of developing quantum computers. Hence, it is reasonable to consider converting such PKE schemes into encryption schemes with additional functionalities. By using existing generic constructions of BC-IBE, those post-quantum PKE schemes are transformed into BC-IBE with non-compact public parameter. In this paper, we propose generic constructions of BC-IBE whose public parameter-size is more compact, and it is possible to apply many post-quantum PKE schemes secure against chosen plaintext attacks, into our generic constructions. To this end, we construct BC-IBE schemes from a group testing perspective, while existing ones are constructed by employing error-correcting codes or cover-free families. As a result, we can obtain BC-IBE schemes with more compact public parameter, which are constructed from the NIST PQC PKE schemes.