Remote sensing is considered to be a key technology for the development of smart cities. By analysing the data obtained by remote sensing, it is effective to manage and develop smart cities. However, with the rapid urbanisation and the increase in data capacity, how to store and retrieve remote sensing data which have more potential value and privacy with a more effective and safe method has become an imminent issue. In this paper, we propose an efficient verifiable and dynamic multi-keyword searchable encryption scheme for remote sensing data in smart cities. Moreover, we construct a double-chain index to support a multi-keyword search, where the Verification Index Chain is used to identify the users and the Keyword Index Chain is used to store the information of keywords. In addition, we adopt extended bitmap technology to realise update operations and verify the correctness and integrity of the search results. Experiments show that compared to the related existing schemes, the search time of the proposed scheme is reduced by 35% at most, the verification time is reduced by 14% at most and the update time is reduced by 57% at most.

The phrase searchable encryption scheme improves search efficiency and accuracy by searching a set of consecutive keywords from ciphertext. However, most current phrase searchable encryption schemes still don't support dynamic data updates in practical application scenarios such as smart healthcare due to forward security issues. In this article, a dynamic forward secure searchable encryption scheme with phrase search for smart healthcare systems is proposed. On the one hand, we adopt a state chain structure to construct an inverted index, which contains the location of keywords so as to achieve phrase search. On the other hand, we have added a modification operation that modifies the location of keywords directly by traversing the inverted index to achieve indexes update. In this way, the efficiency of data updating can be raised greatly because the update operation of first-delete-then-add is avoided in the previous phrase search scheme. The scheme is proved to satisfy the forward security in the leaked search pattern and access pattern since the server cannot know the updated state of updated files in the state chain index structure which is randomly generated by the client. Experimental results show that the proposed scheme has higher search accuracy and efficiency which can save at least 50ms in search time compared to other related schemes.

In an intelligent edge network, data owners encrypt data and outsource it to the edge servers to prevent the leakage of data and user information. It is a research issue to achieve efficient search and data update of the ciphertext stored in the edge servers. For the above problems, we construct a fuzzy multi-keyword search scheme based on a two-level tree index, where the first-level tree index stores keyword tags and the second-level stores encrypted file identifiers and counting bloom filters (CBFs). By constructing a two-level tree index, efficient multi-keyword search is realised, and it also has obvious time advantages when performing the single-keyword search. In addition, the proposed scheme supports index updating by introducing the CBF, and it can realise fuzzy search by calculating the inner product between the CBF in index and search trapdoor. At last, the proposed scheme is proved to be semantically secure under the known ciphertext attack model. Theoretical analysis and simulation test indicate that the proposed scheme spends lower computation overhead than other related schemes, especially in the search phase; as the number of matching files or query keywords grows, it costs less time, at around 2–10 ms.