Conjunctive searchable encryption with efficient authorization for group sharing

Multi-user searchable encryption (MUSE) schemes provide solutions for searching over ciphertexts shared by different users, but the significant overhead of communication and computation leads to high latency in the group sharing system. Moreover, most MUSE schemes support only single-keyword search, and are vulnerable to the internal keyword guessing attack (IKGA). In this paper, to address these challenging tasks, we first propose a dual-server Public-key Puncturable Encryption with Conjunctive Keyword Search (dPPECKS) scheme in a group sharing scenario by extending the Punctrable Encryption (PE) and conjunctive keyword search (CKS) technologies. Our scheme realizes the efficient and dynamic update of team members, including user joining and exiting. Through rigorous analysis, we prove that our scheme can achieve IND-CKA2 security and resist IKGA. Extensive evaluation results demonstrate that our proposed scheme achieves significant improvements in terms of communication and computation costs. For example, compared with prior related work, with 90 people left in a team of 100, the storage cost of ciphertext is reduced from 80 to 1.8 KB. Under the same setting, it costs only 0.177 s to generate the ciphertext in our scheme, which is 90 times less than that in another scheme.