Client-based confidential data sharing using untrusted clouds

Abstract

Cloud storage has been used widely by organizations and individuals. However, using known cloud providers is not a solution that can fit the needs of many entities that need to store private and sensitive data. This is due to the fact that the data stored in the cloud is not hidden from the cloud providers themselves. This issue can be critical for example in use cases including the usage of governmental data, health care and patients data, or even for individual users who are careful about their privacy. A simple solution to this problem can be encrypting the data with a symmetric key before uploading it to the cloud and decrypt to reuse. However, this raises several issues including the lack of the ability to share files with different users. The proposed solution tackles the issue of sharing data confidentially by designing and implementing a system that allows encrypted data sharing and revocation between users. The clouds are considered untrusted where all computations are performed on the client-side with no trusted third party. The scheme is analyzed and the implementation is evaluated and compared to existing solutions showing that it outperforms them. Two practical prototypes were implemented using the proposed scheme including a cloud storage application and an IoT cloud system. Those applications show that the work presented in this thesis is applicable in real-life scenarios