A Novel Two Layer Confidentiality and Authentication Technique for User-Assisted Cooperative NOMA System

User-Assisted Cooperative Non-Orthogonal Multiple Access (UA-CNOMA) is a key enabler for Beyond 5G (B5G) networks, offering efficient spectrum usage by allowing multiple users to share time-frequency resources. This technology holds significant potential for defence and military communications, where secure, reliable, and high-capacity transmission is crucial. This paper introduces a novel two-layer physical layer security (PLS) framework for UA-CNOMA systems, designed to ensure both data confidentiality and user authentication under adversarial conditions. The approach combines chaotic encryption using a logistic map with PLS keys derived from wireless channel characteristics, securing both data and control parameters from tampering or prediction. Physical layer authentication (PLA) is employed by generating unique authentication tags based on channel features, ensuring that only legitimate users gain access. To enhance communication reliability in complex environments, user-assisted relays and successive interference cancellation (SIC) are integrated for effective signal decoding and secure decryption. Performance evaluations, including Bit Error Rate (BER) and security metrics, confirm the scheme’s robustness against eavesdropping and spoofing attacks. The proposed framework provides a scalable, secure, and resilient solution tailored for mission-critical defence applications in modern B5G communication systems.