An algorithm for efficient privacy-preserving item-based collaborative filtering

• We propose an efficient privacy-preserving item-based collaborative filtering method.
• We propose an unsynchronized protocol to achieve secure multi-party computation.
• We propose two incremental privacy-preserving item similarity computation methods.
• The privacy preservation property of the proposed method is formally proved.
• The proposed method is more efficient and accurate than two well-known methods.

Collaborative filtering (CF) methods are widely adopted by existing recommender systems, which can analyze and predict user “ratings” or “preferences” of newly generated items based on user historical behaviors. However, privacy issue arises in this process as sensitive user private data are collected by the recommender server. Recently proposed privacy-preserving collaborative filtering (PPCF) methods, using computation-intensive cryptography techniques or data perturbation techniques are not appropriate in real online services. In this paper, an efficient privacy-preserving item-based collaborative filtering algorithm is proposed, which can protect user privacy during online recommendation process without compromising recommendation accuracy and efficiency. The proposed method is evaluated using the Netflix Prize dataset. Experimental results demonstrate that the proposed method outperforms a randomized perturbation based PPCF solution and a homomorphic encryption based PPCF solution by over 14X and 386X, respectively, in recommendation efficiency while achieving similar or even better recommendation accuracy.