Privacy-preserving data search with fine-grained dynamic search right management in fog-assisted Internet of Things

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Fog computing, as an assisted method for cloud computing, collects Internet of Things (IoT) data to multiple fog nodes on the edge of IoT and outsources them to the cloud for data search, and it reduces the computation cost on IoT nodes and provides fine-grained search right management. However, to provide privacy-preserving IoT data search, the existing searchable encryptions are very inefficient as the computation cost is too high for the resource-constrained IoT ends. Moreover, to provide dynamic search right management, the users need to be online all the time in the existing schemes, which is impractical. In this paper, we first present a new fog-assisted privacy-preserving IoT data search framework, where the data from each IoT device is collected by a fog node, stored in a determined document and outsourced to the cloud, the users search the data through the fog nodes, and the fine-grained search right management is maintained at document level. Under this framework, two searchable encryption schemes are proposed, i.e., Credible Fog Nodes assisted Searchable Encryption (CFN-SE) and Semi-trusted Fog Nodes assisted Searchable Encryption (STFN-SE). In CFN-SE scheme, the indexes and trapdoors are generated by the fog nodes, which greatly reduce the computation costs at the IoT devices and user ends, and fog nodes are used to support offline users’ key update. In STFN-SE scheme, the semi-trusted fog nodes are used to provide storage of encrypted key update information to assist offline users’ search right update. In both schemes, no re-encryption of the keywords is needed in search right updates. The performance evaluations of our schemes demonstrate the feasibility and high efficiency of our system.National Key Research and Development ProgramNational Natural Science Foundation of ChinaSichuan Provincial Major Frontier IssuesState Key Laboratory of Integrated Services Networks, Xidian Universit

Multi-User Dynamic Searchable Symmetric Encryption with Corrupted Participants

We study the problem of multi-user dynamic searchable symmetric encryption (DMUSSE) where a data owner stores its encrypted documents on an untrusted remote server and wishes to selectively allow multiple users to access them by issuing keyword search queries. Specifically, we consider the case where some of the users may be corrupted and colluding with the server to extract additional information about the dataset (beyond what they have access to). We provide the first formal security definition for the dynamic setting as well as forward and backward privacy definitions. We then propose μSE, the first provably secure DMUSSE scheme and instantiate it in two versions, one based on oblivious data structures and one based on update queues, with different performance trade-offs. Furthermore, we extend μSE to support verifiability of results. To achieve this, users need a secure digest initially computed by the data owner and changed after every update. We efficiently accommodate this, without relying on a trusted third party, by adopting a blockchain-based approach for the digests’ dissemination and deploy our schemes over the permissioned Hyperledger Fabric blockchain. We prototype both versions and experimentally evaluate their practical performance, both as stand-alone systems and running on top of Hyperledger Fabric

USER PERCEPTIONS OF AND ATTITUDES TOWARD ENCRYPTED COMMUNICATION

As people rely more heavily on online communication, privacy becomes an increasingly critical concern. Users of communication services (e.g., email and messaging) risk breaches of confidentiality due to attacks on the service from outsiders or rogue employees, or even government subpoenas and network surveillance. End-to-end encryption, in which anyone cannot read the user's content, is the only way to fully protect their online communications from malicious attackers, rogue company employees, and government surveillance. Although in recent years we have witnessed considerable efforts to push end-to-end encryption into broader adoption, and indeed several popular messaging tools have adopted end-to-end encryption, some obstacles still remain which hinder general users from proactively and confidently adopting end-to-end encrypted communication tools and acknowledge their security benefits. In this dissertation, we investigated the adoption of end-to-end encrypted communication from a variety of user-centered perspectives. In the first part, we conducted a lab study (n=52), evaluating how general users understand the balance between the usability and security for different key management models in end-to-end encryption. We found that participants understood the models well and made coherent assessments about when different tradeoffs might be appropriate. Our participants recognized that the less-convenient exchange model was more secure overall, but found the security of the key-directory based model to be "good enough" for many everyday purposes. In the second part, we explored how general users value the usability and security tradeoffs for different approaches of searching over end-to-end encrypted messages. After systematizing these tradeoffs to identify key feature differences, we used these differences as a basis for a choice-based conjoint analysis experiment (n=160). We found that users indicated high relative importance for increasing privacy and minimizing local storage requirements. While privacy was more important overall, after the initial improvement was made, further improvement was considered less valuable. Also, local storage requirement was more important than adding marginal privacy. Since significant research indicated that non-expert users' mental models about end-to-end encryption led them to make mistakes when using these tools, in the third part of this dissertation, we took the first step to tackle this problem by providing high-level, roughly correct information about end-to-end encryption to non-expert users. In a lab study, participants (n=25) were shown one of several variations on a short tutorial. Participants were asked about their understanding of end-to-end encryption before and after the tutorial, as well as which information they found most useful and surprising. Overall, participants effectively learned many benefits and limitations of end-to-end encryption; however, some concerns and misconceptions still remained, and our participants even developed new ones. The results provided insight into how to structure new educational materials for end-to-end encryption