Key updatable public key encryption with keyword search (Or: How to realize PEKS with efficient key updates for IoT environments)
Security and privacy are the key issues for the Internet of Things (IoT) systems. Especially, secure search is an important functionality for cooperation among users' devices and non trusted servers. Public key encryption with keyword search (PEKS) enables us to search encrypted data and is expected to be used between a cloud server and users' mobile devices or IoT devices. However, those mobile devices might be lost or stolen. For IoT devices, it might be difficult to store keys in a tamper proof manner due to prohibitive costs. In this paper, we deal with such a key exposure problem on PEKS and introduce the concept of PEKS with key updating functionality, which we call key updatable PEKS (KU PEKS) Specifically, we propose two models of KU PEKS: the key evolution model and the key insulation model In the key evolution model, a pair of public and secret keys can be updated if needed (e.g. the secret key is exposed) In the key insulation model, the public key remains fixed while the secret key can be updated if needed. The former model makes a construction simple and more efficient than the latter. On the other hand, the latter model is preferable for practical use since a user never updates their public key. We show constructions in each model in a black box manner. We also give implementation results on Raspberry Pi 3, which can be regarded as a reasonable platform of IoT devices.
International Journal of Information Security