Privacy Preserving User-based Recommender System
Shahriar Badsha, Xun Yi, Ibrahim Khalil and Elisa Bertino
RMIT University, RMIT University, RMIT University, Purdue University

With the rapid development of the social networks, Collaborative Filtering (CF)-based recommender systems have been increasingly prevalent and become widely accepted by users. The CF-based techniques generate recommendations by collecting privacy sensitive data from users. Usually, the users are sensitive to disclosure of personal information and consequently, there are unavoidable security concerns since private information can be easily misused by malicious third parties. In order to protect against breaches of personal information, it is necessary to obfuscate user information by means of an efficient encryption technique while simultaneously generating the recommendation by making true information inaccessible to service providers. Therefore, we propose a privacy preserving user-based CF technique based on homomorphic encryption, which is capable of determining similarities among users followed by generating recommendations without revealing any private information. We introduce different semi-honest parties to preserve privacy and to carry any intermediate computations for generating recommendations. We implement our method on publicly available datasets and show that our method is both practical and able to achieve a high level of security for users without compromising the accuracy of recommendations.