CenPush: Blocking-Resistant Control Channel Using Push Notifications
Authors: Piyush Kumar Sharma (University of Michigan), Diwen Xue (University of Michigan), Aaron Ortwein (University of Michigan), Cecylia Bocovich (The Tor Project), Harry (Independent), Roya Ensafi (University of Michigan)
Volume: 2025
Issue: 4
Pages: 712–727
DOI: https://doi.org/10.56553/popets-2025-0153
Abstract: The rapid increase in global censorship events has stimulated a substantial growth in users relying on circumvention tools. Fighting against censors requires tool maintainers to frequently update client-side configurations and proxy IPs. However, existing methods for doing so require clients to explicitly query for updates. Further, this client-initiated communication relies mostly on ad-hoc and out-of-band channels. This work demonstrates the utility of push notification services as an efficient and sustainable communication channel between tool maintainers and their clients. A push notification channel allows tool maintainers to update client configurations automatically without the need for clients to initiate a query themselves. We develop a general-purpose design for integrating push notifications as a control channel in circumvention tools. We utilize the design to integrate and implement push notifications for use in the popular circumvention tool Tor and demonstrate their utility to push bridge line updates to Tor clients.
Keywords: Censorship, Blocking Resistance, Push Notification, Tor
Copyright in PoPETs articles are held by their authors. This article is published under a Creative Commons Attribution 4.0 license.
