Explore the security implications of Sigfox, a low-power wide-area network technology for IoT devices, in this 38-minute conference talk from the 35th Chaos Communication Congress. Dive deep into the radio protocol analysis, including the dissection of uplink and downlink structures, and learn about the open reference implementation of an alternative Sigfox protocol stack. Discover why certain applications may be suitable for Sigfox while others should be avoided. Gain insights into radio technology basics, protocol analysis techniques, and potential security vulnerabilities. Understand the importance of independent security audits for proprietary protocols and explore suggestions for improving Sigfox's security. Suitable for a technical audience with basic cryptography knowledge, this talk provides valuable information on IoT network security without requiring extensive RF technology expertise.