Journey to the Center of PSTN - I Became a Phone Company. You Should Too

Explore the inner workings of the Public Switched Telephone Network (PSTN) in this 44-minute DEF CON 33 conference talk that demystifies one of the world's most essential yet opaque communication systems. Begin with a historical overview of the PSTN before diving deep into its technical architecture and regulatory frameworks that govern telecommunications networks. Learn how large corporations dominate this space through deliberately complex structures, then follow a practical, first-hand guide to forming your own local exchange carrier to serve your community. Discover the complete process from obtaining regulatory approval and building PSTN interconnections to designing voice networks while prioritizing user security and privacy. Examine various network exploits including methods to bypass STIR/SHAKEN protocols, techniques for number hijacking, and how telecommunications fraud operates and generates revenue. Conclude with insights into the PSTN's future evolution and emerging security challenges facing this critical infrastructure that connects billions of users worldwide through cellular networks, SIP trunks, and traditional POTS lines.