Towards practical quantum key distribution. Security and integration in modern communication systems

Encryption enables confidential communication over a public communication channel. To encrypt a message, a cryptographic key is required. Quantum key distribution (QKD) is a method based on the laws of quantum physics for establishing the cryptographic keys used by an encryption system. The results presented in this dissertation demonstrate that QKD can be implemented as part of modern communication networks and can generate key material suitable for use with contemporary cryptographic algorithms.

However, the distinctive nature of QKD, compared with conventional key-exchange techniques, poses specific challenges for its secure deployment in modern communication networks. These challenges include the limited reach of communication links and their sensitivity to background noise, restrictions on network topologies, and the requirement to distribute authentication keys through mechanisms external to the QKD system itself.

This dissertation addresses these issues through four included publications. The first part examines the foundations of QKD security. The second part investigates the integration of QKD into modern communication networks from four perspectives: network infrastructure, authentication-key distribution, communication channels, and the cryptographic systems used by end users. The results elucidate the conditions under which the security guarantees offered by QKD can be realized in modern communication networks, as well as the efficiency with which these guarantees can be achieved.