As space-division multiplexing (SDM) emerges as a transformative technology in elastic optical networks (EONs), ensuring secure and efficient spectrum allocation becomes increasingly critical. This paper proposes a hybrid secure spectrum allocation framework that combines cryptographic authentication, game-theoretic modeling, and heuristic optimization to enhance both performance and protection in SDM-enabled EONs. The proposed framework dynamically allocates spectrum resources while mitigating risks such as eavesdropping, jamming, and denial-of-service attacks. Simulation results on standard network topologies demonstrate the framework’s ability to maintain high spectral efficiency, minimize blocking probability, and resist common security threats. This research contributes a novel intersection of physical-layer security and resource management in next-generation optical networks.