Comparison of security mechanisms of Mathematical cipher, Wyner scheme, QKD, and Quantum stream cipher

A new generation of global communications technology has been emerging. These systems, which utilize established device technologies and quantum effect devices, require ultra-high speeds, low cost, and strong security. In recent years, global communication systems have faced various practical security challenges depending on their configurations, and research efforts are underway to address these issues. In particular, the issue of the security of physical layer security from microwave wireless systems to quantum optical communication systems is urgent problem. However, concepts of cryptographic schemes have also been diversifying. Typical examples are mathematical ciphers, the Wyner scheme and QKD. Then, the Y-00 protocol has recently emerged as a third pillar cryptographic technology in the optical quantum domain. These security principles differ significantly from one another. This makes it difficult for different fields to understand each other. At this stage, comparative explanations of the security principles underlying these various cryptographic technologies are likely to promote mutual understanding among researchers across different fields. As the first trial, this lecture note explains the security mechanism of the third pillar (Y-00), comparing it with the principles of other mechanisms.