ANONYCALL: Enabling Native Private Calling in Mobile Networks
Hexuan Yu
Network and Distributed System Security (NDSS) Symposium 2026 · Day 2 · Network Security
Hexuan Yu, a PhD candidate from Virginia Tech, presents ANONYCALL, a system that enables truly private phone calls within existing **5G cellular infrastructure** without requiring modifications to the IMS signaling process, RAN components, or core network logic. The system solves two critical problems that prevent anonymous cellular access from being practical: how to make an anonymous user reachable by phone (when the operator does not know who they are) and how to bill an anonymous user for usage without breaking their privacy. ANONYCALL introduces **temporary short-lived CP-URIs** that decouple identity from reachability, combined with a novel **privacy-preserving charging credential** using Pedersen commitments and adaptable signatures. The complete system adds less than **200 milliseconds** of overhead to a standard 5G call setup, making it imperceptible to users. The work is motivated by the privacy needs of military personnel, government employees, and other sensitive persons whose location can be persistently tracked through cellular network metadata.
AI review
A well-designed privacy system for cellular communications that actually solves the practical barriers (reachability and billing) preventing anonymous phone calls from being deployable. Sub-200ms overhead on a real 5G IMS core is genuinely practical. The Pedersen commitment-based billing and conditional unlinkability are cryptographically clean. Not an offensive talk, but demonstrates real understanding of the operational problem space for sensitive personnel.