A high-bandwidth, low-latency system for anonymous broadcasting

Abstract

In this thesis,1 we design and evaluate Spectrum, a system for bandwidth efficient, anonymous broadcasting. In this system, one (or more) publishers broadcast a message to many users, who provide cover traffic. These users share their message between two or more servers; as long as one of these is honest, even an adversary with a complete view of the network cannot discover a message's source. Prior systems require that each user publish a message; however, streaming media tends to have many consumers for every content producer. We take advantage of this for a large performance improvement. To do so, we provide a cryptographic solution to the disruption problem, where dishonest users can corrupt a message by writing noise. This solution provides access control for operations performed obliviously by the servers. Spectrum is 60x faster than prior work for moderate-sized messages (10 kB), Each client uploads under 1 kB of additional data to broadcast a message of any size. Using a two-server deployment, Spectrum is fast enough to broadcast 3.4 GB/h to 600 users or streaming video to 5,000 users. Further, we can shard Spectrum across many physical servers for commensurate speedup, scaling a given workload to many more users.