  Multi-access edge computing (MEC) has been regarded as a promising technique
for enhancing computation capabilities for wireless networks. In this paper, we
study physical layer security in an MEC system where multiple users offload
partial of their computation tasks to a base station simultaneously based on
non-orthogonal multiple access (NOMA), in the presence of a malicious
eavesdropper. Secrecy outage probability is adopted to measure the security
performance of the computation offloading against eavesdropping attacks. We aim
to minimize the sum energy consumption of all the users, subject to constraints
in terms of the secrecy offloading rate, the secrecy outage probability, and
the decoding order of NOMA. Although the original optimization problem is
non-convex and challenging to solve, we put forward an efficient algorithm
based on sequential convex approximation and penalty dual decomposition.
Numerical results are eventually provided to validate the convergence of the
proposed algorithm and its superior energy efficiency with secrecy
requirements.
