Lightweight Access Delegation With Multi-Ciphertext Equivalence Test for Shared Data in ITS

The content-centric data sharing in Intelligent Transportation Systems (ITS) becomes increasingly imperative to improve road safety and traffic efficiency. In order to protect the privacy of vehicle users, data is generally encrypted prior to being shared, whereas it hinders data searching and utilization. Proxy re-encryption with equivalence test (PREET) has been proposed to test the equivalence between encrypted messages, and to delegate the decryption right of searched data to the specified user. However, existing PREET schemes primarily focus on the equivalence test between two ciphertexts, which aren't suitable for the most practical scenarios that more than two ciphertexts need to be verified, due to the exposure of users' extra information and the redundant computation. In this paper, to tackle these problems, we present a lightweight certificateless proxy re-encryption with multi-ciphertext equivalence test (CL-PREMET) for shared data to address the data search and authorized utilization over encrypted data in ITS. In our design, the users are allowed to efficiently and accurately search over massive encrypted data based on flexible multi-ciphertext analysis and to utilize their own keys rather than data owner's key to decrypt the searched data after being authorized, without revealing any private and sensitive information. The CL-PREMET achieves the IND-CCA security and the OW-CCA security. Furthermore, the simulation experiment displays that the CL-PREMET is feasible. Compared with existing PREET schemes, in addition to being suitable for multi-ciphertext equivalence analysis, our scheme leverages the certificateless public key cryptography (CL-PKC) to avoid certificate management and key escrow problems.