Do not tell me what I cannot do! (The constrained device shouted under the cover of the fog): Implementing Symmetric Searchable Encryption on Constrained Devices

Symmetric Searchable Encryption (SSE) allows the outsourcing of encrypted data to possible untrusted third
party services while simultaneously giving the opportunity to users to search over the encrypted data in a
secure and privacy-preserving way. Currently, the majority of SSE schemes have been designed to fit a typical
cloud service scenario where users (clients) encrypt their data locally and upload them securely to a remote
location. While this scenario fits squarely the cloud paradigm, it cannot apply to the emerging field of Internet
of Things (IoT). This is due to the fact that the performance of most of the existing SSE schemes has been
tested using powerful machines and not the constrained devices used in IoT services. The focus of this paper
is to prove that SSE schemes can, under certain circumstances, work on constrained devices and eventually
be adopted by IoT services. To this end, we designed and implemented a forward private dynamic SSE
scheme that can run smoothly on resource-constrained devices. To do so, we adopted a fog node scenario
where edge (constrained) devices sense data, encrypt them locally and use the capabilities of fog nodes to
store sensed data in a remote location (the cloud). Consequently, end users can search for specific keywords
over the stored ciphertexts without revealing anything about their content. Our scheme achieves efficient
computational operations and supports the multi-client model. The performance of the scheme is evaluated by
conducting extensive experiments. Finally, the security of the scheme is proven through a theoretical analysis
that considers the existence of a malicious adversary.