Secret Key Extraction from Observations of an Almost Reciprocal Radio Channel

In times of increasing connectivity, autonomous systems and wireless data transfer, security and privacy are becoming the most significant factor for the consumer acceptance of technology. Securing a communication channel is a well-understood challenge with various well-established solutions. However, Physical Layer Security introduces novel concepts not just adding another layer of security to communication systems. It also provides solutions which are suitable for special constraints known from, e.g., the Internet of Things and sensor networks. While Physical Layer Security has been recognized for some time already, efforts to find practical solutions have only become noteworthy in recent years. Particularly the extraction of secret keys from reciprocal communication channels has encouraged many researchers to present different concepts, algorithms and results in the field of efficient key generation. Nevertheless, due to a lack of common evaluation frameworks with clear parameterization, joint system architecture and meaningful definition of performance metrics, a fair analysis and comparison of presented schemes is hardly possible. This dissertation focuses on practical aspects of secret key generation. Based on a systematic analysis, a modular reference architecture comprising various building blocks is proposed. The consideration of an attacker, definition of suitable performance metrics and results from simulations and from measurements using an off-the-shelf implementation provide insights into the technology's applicability. The proposal and analysis of novel concepts of high practical relevance opens up further possibilities for future advances and optimization of the overall security concept.