Summary Understanding of any computing environment requires familiarity with its underlying technologies. Internet of Things (IoT), being a new era of computing in the digital world, aims for the development of large number of smart devices that would support a variety of applications and services. These devices are resource‐constrained, and the services they would provide are going to impose specific requirements, among which security is the most prominent one. Therefore, in order to comprehend and conform these requirements, there is a need to illuminate the underlying architecture of IoT and its associated elements. This comprehensive survey focuses on the security architecture of IoT and provides a detailed taxonomy of major challenges associated with the field and the key technologies, including Radio Frequency Identification (RFID) and Wireless Sensor Networks (WSN), that are enabling factors in the development of IoT. The paper also discusses some of the protocols suitable for IoT infrastructure and open source tools and platforms for its development. Finally, a brief outline of major open issues, along with their potential solutions and future research directions, is given.