The Trials and Tribulations of Building Your Own Phone

The talk opens with the case for building a phone rather than buying one. The speaker argues that smartphones and mobile networks expose location, contacts, and browsing data, pointing to SS7 weaknesses, cell-site simulators, data brokers, and ad-tech tracking. Privacy and a wish to step back from constant connectivity drove the project, which the speaker presents as an unfinished journey rather than a guide.

The modem came first. Datasheets sat behind registration forms, and one sales contact claimed carrier certification was required, though it never was. The speaker settled on a SIM7600 module over a certified system-on-module. A first custom breakout board with antenna connectors, a SIM slot, audio, and level shifters did not power on, so a Raspberry Pi hat was used in the meantime. The software layer was a Rust service that talked to the modem over serial using the Hayes command set, until the speaker found that ModemManager already handled that work. Planned features include a standalone Linux device, Signal-based messaging, encryption of data at rest, hardware switches to cut power to the modem and microphone, and stingray detection.

The project remains early, with no formal contribution channels yet. The speaker plans to post updates and slides on a personal site and invites feedback. For practitioners, the talk shows that RF board work is more approachable when vendor reference designs are followed, and that existing system services should be checked before writing new ones. Open questions raised in Q&A include whether silent SMS could be detected, how to handle battery life, and which form factor to pursue.