Sean Mulvany, Ph.D Technology Transfer Case Manager Privacy ensuring recommender system Sean Mulvany, Ph.D Technology Transfer Case Manager Trinity Research & Innovation
Trinity College Dublin, the University of Dublin, Dublin 2, Ireland.
 +353 86 3181881 +353 1 896 4985 sean.mulvany@tcd.ie @seanmulvany

OVERVIEW Currently Users rate some items (directly, by clicking, buying, viewing, pairwise comparison etc), task of the recommender is to predict their ratings for other items of interest. The pattern of item ratings supplied by a user by itself can identify that user, even if not explicitly tagged with a user id. Already demonstrated in the wild e.g. netflix/IMDB de-anonymisation attack. Privacy/data protection concerns, e.g. in EU, mean: User ratings data, even if anonymised by removing user IDs, cannot be used for other purposes or sold to third parties Inadvertent release of ratings data, e.g. due to mishap or hacking, carries excessive privacy and reputational risk Growing user unease

BLC Private Recommender BLC Uses Shared Identities (“nyms”) For Privacy Users rate items as before, e.g. in app or browser. But now app/browser selects a shared identity/nym and submits ratings using this The system only ever sees/stores (nym, item, rating) information. A “hiding in the crowd” type of privacy, which comes with strong guarantees. Even if nym used by user is inadvertently disclosed, items rated by user are not revealed. Easily understood by users No degradation in prediction performance, no need to add “noise” to ratings to gain privacy

Excellent Recommendation Performance Shared Identities Improve Prediction Performance As Well As Privacy It is already widely recognised, e.g. by advertisers, that users can be grouped into categories by taste, demographic, location etc Grouping boosts the prediction performance of collaborative filters, if groups are chosen well, since users sharing a group are much more alike than the general population. State of the art performance “out of the box”, no fine-tuning

Thank You http://www.tcd.ie/research_innovation/ http://www.tcd.ie/research_innovation/technology/