  As publishers increasingly use Content Distribution Networks (CDNs) to
distribute content across geographically diverse networks, CDNs themselves are
becoming unwitting targets of requests for both access to user data and content
takedown. From copyright infringement to moderation of online speech, CDNs have
found themselves at the forefront of many recent legal quandaries. At the heart
of the tension, however, is the fact that CDNs have rich information both about
the content they are serving and the users who are requesting that content.
This paper offers a technical contribution that is relevant to this ongoing
tension with the design of an Oblivious CDN (OCDN); the system is both
compatible with the existing Web ecosystem of publishers and clients and hides
from the CDN both the content it is serving and the users who are requesting
that content. OCDN is compatible with the way that publishers currently host
content on CDNs. Using OCDN, publishers can use multiple CDNs to publish
content; clients retrieve content through a peer-to-peer anonymizing network of
proxies. Our prototype implementation and evaluation of OCDN show that the
system can obfuscate both content and clients from the CDN operator while still
delivering content with good performance.
