  The exploitation of user search queries by search engines is at the heart of
their economic model. As consequence, offering private Web search
functionalities is essential to the users who care about their privacy.
Nowadays, there exists no satisfactory approach to enable users to access
search engines in a privacy-preserving way. Existing solutions are either too
costly due to the heavy use of cryptographic mechanisms (e.g., private
information retrieval protocols), subject to attacks (e.g., Tor, TrackMeNot,
GooPIR) or rely on weak adversarial models (e.g., PEAS). This paper introduces
X-Search , a novel private Web search mechanism building on the disruptive
Software Guard Extensions (SGX) proposed by Intel. We compare X-Search to its
closest competitors, Tor and PEAS, using a dataset of real web search queries.
Our evaluation shows that: (1) X-Search offers stronger privacy guarantees than
its competitors as it operates under a stronger adversarial model; (2) it
better resists state-of-the-art re-identification attacks; and (3) from the
performance perspective, X-Search outperforms its competitors both in terms of
latency and throughput by orders of magnitude.
