  A large spectrum of technologies are collectively dubbed as physical layer
security (PLS), ranging from wiretap coding, secret key generation (SKG),
authentication using physical unclonable functions (PUFs), localization / RF
fingerprinting, anomaly detection monitoring the physical layer (PHY) and
hardware. Despite the fact that the fundamental limits of PLS have long been
characterized, incorporating PLS in future wireless security standards requires
further steps in terms of channel engineering and pre-processing. Reflecting
upon the growing discussion in our community, in this critical review paper, we
ask some important questions with respect to the key hurdles in the practical
deployment of PLS in 6G, but also present some research directions and possible
solutions, in particular our vision for context-aware 6G security that
incorporates PLS.
