Rollercoaster: An efficient group-multicast scheme for mix networks

Conference Object
Change log
Hugenroth, D 
Beresford, AR 

Mix network designs such as Loopix provide strong metadata anonymity guarantees that are crucial across many applications. However, because they limit the rate at which messages can be sent by each user, they incur high delays when sending many messages to multiple recipients – for instance, in decentralised collaborative apps.In this paper we present an efficient multicast scheme named Rollercoaster that reduces the time for delivering a message to all members of a group of size m from O(m) to O(log m). Rollercoaster can be deployed without modifications to the underlying mix network, allowing it to benefit from the anonymity set provided by existing users. We further develop an extension that achieves the same asymptotic guarantees in the presence of unreliable group members.While the scheme is applicable to many mix network de-signs, we evaluate it for the Loopix network, which is the most advanced and practical design to date. For this evaluation we developed a network simulator that allows fast, reproducible, and inspectable runs while eliminating external influences.

Journal Title
Proceedings of the 30th USENIX Security Symposium
Conference Name
30th USENIX Security Symposium
Journal ISSN
Volume Title
USENIX Association
Publisher DOI
Engineering and Physical Sciences Research Council (EP/M020320/1)
Isaac Newton Trust (19.08(m))
Leverhulme Trust (ECF-2019-028)
Daniel Hugenroth is supported by a Nokia Bell Labs Scholarship and the Cambridge European Trust. Martin Kleppmann is supported by a Leverhulme Trust Early Career Fellowship, the Isaac Newton Trust, Nokia Bell Labs,and crowdfunding supporters including [...]. Alastair R. Beresford is partially supported by EPSRC [grantnumber EP/M020320/1].