Chapter 2 · General information about cryptography
This chapter supplies the theoretical groundwork needed to compare physical key-distribution methods. It distinguishes mathematical cryptography, which relies on assumptions about hard problems, from physical cryptography, which seeks security properties rooted in physics. The chapter makes clear that all physical methods discussed in the book generate or distribute symmetric keys only.
It then explains the three key technologies at a high level: QKD, RKD, and MKD. QKD relies on quantum effects and, depending on the variant, external randomness or entanglement-derived randomness. RKD uses reciprocal radio-channel properties and physical randomness from propagation effects. MKD uses external non-deterministic random generators and physically transports key material on storage media.
The chapter also discusses how key distribution differs within a pair and across multiple communication partners, introducing trusted nodes as a scaling mechanism for QKD and RKD. Finally, it defines the core protection goals: confidentiality, integrity, and authenticity. A central point is that mathematically provable confidentiality is achieved only with the one-time pad, while physical methods can support highly secure symmetric schemes for confidentiality, integrity, and authenticity.
- Defines mathematical vs physical cryptography
- Explains QKD, RKD, and MKD fundamentals
- Introduces trusted nodes and multi-party distribution
- Clarifies confidentiality, integrity, authenticity
- Establishes Alice, Bob, Eve, and Mallory roles