Privacy-preserving machine learning techniques

Machine Learning as a Service (MLaaS) refers to a service that enables companies to delegate their machine learning tasks to single or multiple untrusted but powerful third parties, namely cloud servers. Thanks to MLaaS, the need for computational resources and domain expertise required to execute machine learning techniques is significantly reduced. Nevertheless, companies face increasing challenges with ensuring data privacy guarantees and compliance with the data protection regulations. Executing machine learning tasks over sensitive data requires the design of privacy-preserving protocols for machine learning techniques. In this thesis, we aim to design such protocols for MLaaS and study three machine learning techniques: Neural network classification, trajectory clustering, and data aggregation under privacy protection. In our solutions, our goal is to guarantee data privacy while keeping an acceptable level of performance and accuracy/quality evaluation when executing the privacy-preserving variants of these machine learning techniques. In order to ensure data privacy, we employ several advanced cryptographic techniques: Secure two-party computation, homomorphic encryption, homomorphic proxy re-encryption, multi-key homomorphic encryption, and threshold homomorphic encryption. We have implemented our privacy-preserving protocols and studied the trade-off between privacy, efficiency, and accuracy/quality evaluation for each of them.