The problem it solves
With more data being pushed to external cloud storage, privacy concerns are usual. Straightforward encryption of uploaded data strips the ability to search over it with some keywords: a highly desirable ability in some use-cases as EMR (Electronic medical records) and IIoT (Industrial Internet of Things). Consequent efforts at constructing post-quantum searchable encryption schemes have failed to resist a curious server launching inside offline keyword guessing attack. Moreover, for every intended receiver, the data owner performs computation separately, implying prior knowledge about recipients. In use-cases, such as EMR, prior knowledge of intended recipients (medical centers) is not true. In this work, we propose a forward-secure searchable encryption scheme that leverages blockchain to take the burden of repetitive computations off the data owner. The proposed scheme resists attacks from an honest-but-curious server and protects the privacy of searches performed.
Challenges we ran into
The scheme is researched and developed by the team members, coming up with such a secure scheme with low computation which a phone's processor can handle was something that we invested a lot of time into. Another challenge for us was to integrate c++ as the backend of a flutter app which required us to do a lot of interfacing work. Besides that, It took us an immense amount of time to actually implement the algorithms which involved a lot of work-related to lattice-based cryptography and optimizing them for mobile processors.