Secure and Privacy-Preserving Cloud-Assisted Computing

Sammanfattning: Smart devices such as smartphones, wearables, and smart appliances collect significant amounts of data and transmit them over the network forming the Internet of Things (IoT). Many applications in our daily lives (e.g., health, smart grid, traffic monitoring) involve IoT devices that often have low computational capabilities. Subsequently, powerful cloud servers are employed to process the data collected from these devices. Nevertheless, security and privacy concerns arise in cloud-assisted computing settings. Collected data can be sensitive, and it is essential to protect their confidentiality. Additionally, outsourcing computations to untrusted cloud servers creates the need to ensure that servers perform the computations as requested and that any misbehavior can be detected, safeguarding security. Cryptographic primitives and protocols are the foundation to design secure and privacy-preserving solutions that address these challenges. This thesis focuses on providing privacy and security guarantees when outsourcing heavy computations on sensitive data to untrusted cloud servers. More concretely, this work: (a)  provides solutions for outsourcing the secure computation of the sum and the product functions in the multi-server, multi-client setting, protecting the sensitive data of the data owners, even against potentially untrusted cloud servers; (b)  provides integrity guarantees for the proposed protocols, by enabling anyone to verify the correctness of the computed function values. More precisely, the employed servers or the clients (depending on the proposed solution) provide specific values which are the proofs that the computed results are correct; (c)  designs decentralized settings, where multiple cloud servers are employed to perform the requested computations as opposed to relying on a single server that might fail or lose connection; (d)  suggests ways to protect individual privacy and provide integrity. More pre- cisely, we propose a verifiable differentially private solution that provides verifiability and avoids any leakage of information regardless of the participa- tion of some individual’s sensitive data in the computation or not.