Public-Key Inverted-Index Keyword Search With Designated Tester and Multiuser Key Decryption in IoT.

Searchable encryption for Cloud-based Internet of Things has been widely explored with the increasing popularity of cloud computing. The public-key encryption with keyword search (PEKS) system support multiuser retrieval. However, the PEKS search time is linearly increasing as the index keyword number growth, and the search time would be huge if the index keywords consistently increase. In this article, we introduce a novel scheme named as public-key inverted-index keyword search with designated tester and multiuser key decryption (IDPEKS). First of all, we design an inverted index based on B-plus tree to reduce the search time to a logarithmic level. On this basis, we optimized the TF-IDF formula and added user preference factor and font size factor to make the relevance score calculation more consistent with needs of receiver. Besides, we design a multiuser key decryption algorithm to protect the system symmetric key. In addition, we set index server to perform the index-trapdoor retrieval process. The designated index server tester can resist the attack of the cloud server on keywords. The security proof shows that the scheme can resist the chosen keyword attack (CKA), keyword guessing attack (KGA), and key guessing attack (KeyGA). The experimental results show that the algorithm can improve retrieval efficiency while have a short encryption time.