  With the emergence of 5G low latency applications, such as haptics and V2X,
low complexity and low latency security mechanisms are sought. Promising
lightweight mechanisms include physical unclonable functions (PUF) and secret
key generation (SKG) at the physical layer, as considered in this paper. In
this framework we propose i) a novel authenticated encryption using SKG; ii) a
combined PUF / SKG authentication to reduce computational overhead; iii) a
0-RTT resumption authentication protocol; iv) pipelining of the SKG and the
encrypted data transfer. With respect to the latter, we investigate a parallel
SKG approach for multi-carrier systems, where a subset of the subcarriers are
used for SKG and the rest for data transmission. The optimal resource
allocation is identified under security, power and delay constraints, by
formulating the subcarrier allocation as a subset-sum $0-1$ knapsack
optimization problem. A heuristic approach of linear complexity is proposed and
shown to incur negligible loss with respect to the optimal dynamic programming
solution. All of the proposed mechanisms, have the potential to pave the way
for a new breed of latency aware security protocols.
