  Sixth generations (6G) systems will be required to meet diverse constraints
in an integrated ground-air-space global network. In particular, meeting overly
aggressive latency constraints, operating in massive connectivity regimes, with
low energy footprint and low computational effort, while providing explicit
security guarantees, can be challenging. In this setting, quality of security
(QoSec) is envisioned as a flexible security framework for future networks with
highly diverse non-functional requirements. Mirroring the differentiated
services (DiffServ) networking paradigm, different security levels could be
conceptualized, moving away from static security controls, captured currently
in zero-trust security architectures. In parallel, the integration of
communications and sensing, along with embedded (on-device) AI, can provide the
foundations for building autonomous and adaptive security controls,
orchestrated by a vertical security plane in coordination with a vertical
semantic plane. It is in this framework, that we envision the incorporation of
physical layer security (PLS) schemes in 6G security protocols, introducing
security controls at all layers, for the first time.
