Efficient data confidentiality scheme for 5G wireless NOMA communications

Non-Orthogonal Multiple Access (NOMA) has recently emerged as a promising multiple access technique for current and future mobile communication networks. Unlike conventional multiple access schemes, NOMA exploits the power domain to service a large number of users at different power levels, using the same time-frequency resources. However, this technology suffers from major security threats since users are able to decode the messages of other paired users utilizing the same resources. In this paper, we propose an efficient and lightweight cipher scheme for NOMA systems at the physical layer. Unlike previous schemes in the literature, the proposed solution combines cryptography and Physical Layer Security (PLS) to provide robust security at minimum cost by adopting a structure that requires a single round with a single operation. Moreover, it is generic in the sense that any simple cipher operation such as permutation, substitution, phase shuffling, or pseudo-random masking, can be utilized in order to secure the underlying NOMA frame symbols. Also, we propose a dynamic key derivation scheme that benefits from the dynamic properties of wireless channels. Simulation results and cryptanalysis show that the proposed solution achieves the desired security level and strikes a good balance between performance and security level.