Privacy-preserving matrix factorization

  • Authors:

  • Valeria Nikolaenko;Stratis Ioannidis;Udi Weinsberg;Marc Joye;Nina Taft;Dan Boneh

  • Affiliations:

  • Stanford, Stanford, California, USA;Technicolor, Palo Alto, California, USA;Technicolor, Palo Alto, California, USA;Technicolor, Renne, France;Technicolor, Palo Alto, California, USA;Stanford, Stanford, California, USA

  • Venue:
  • Proceedings of the 2013 ACM SIGSAC conference on Computer & communications security
  • Year:
  • 2013

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Abstract

Recommender systems typically require users to reveal their ratings to a recommender service, which subsequently uses them to provide relevant recommendations. Revealing ratings has been shown to make users susceptible to a broad set of inference attacks, allowing the recommender to learn private user attributes, such as gender, age, etc. In this work, we show that a recommender can profile items without ever learning the ratings users provide, or even which items they have rated. We show this by designing a system that performs matrix factorization, a popular method used in a variety of modern recommendation systems, through a cryptographic technique known as garbled circuits. Our design uses oblivious sorting networks in a novel way to leverage sparsity in the data. This yields an efficient implementation, whose running time is O(Mlog^2M) in the number of ratings M. Crucially, our design is also highly parallelizable, giving a linear speedup with the number of available processors. We further fully implement our system, and demonstrate that even on commodity hardware with 16 cores, our privacy-preserving implementation can factorize a matrix with 10K ratings within a few hours.