International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 22 May 2015

Trinabh Gupta, Natacha Crooks, Srinath Setty, Lorenzo Alvisi, Michael Walfish
ePrint Report ePrint Report
This paper describes the design, implementation, and experimental evaluation of Popcorn, a media content delivery system that comprehensively hides (even from the content distributor) what is consumed but not necessarily who is doing the consumption. The motivation for Popcorn is both principled and pragmatic: we want to provide provable privacy while still respecting the current commercial context. To instantiate Popcorn, we turn to a powerful primitive from cryptography: private information retrieval (PIR). However, the cost and structure of PIR, as it appears in the literature, present major obstacles to using PIR as the foundation for an Internet-scale service. Nevertheless, with careful system design, and by composing a series of novel refinements and optimizations that leverage the properties of PIR protocols as well as the properties of media streaming, we have produced a system that cheaply hides media consumption, scales to the size of Netflix\'s library (8,000 movies) and respects current controls on media dissemination. The per-request cost in Popcorn is less than three times the per-request cost in a baseline system that does not provide privacy.

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