Nonorthogonal group encryption code index modulation scheme based on reversible cellular automata

To meet the high-rate communication and strong security communication requirements of 6G networks, a nonorthogonal grouping encryption code index modulation (NGECIM) scheme based on reversible cellular automata for code index modulation technology was proposed. A hybrid reversible elementary cellular automata (HRECA) was constructed, which enhanced the randomness of the sequence through multi-rule expansion, XOR operations, and sequence reverse iteration. The information flow was divided into modulation blocks and mapping blocks. After grouping, the modulation blocks were encrypted using cellular automata, with the iteration rules and spreading codes determined by the mapping blocks. Simulation results show that the proposed scheme improves the error rate performance by approximately 0.3~9 dB compared to existing schemes. The key space reaches 2²⁰⁹, and the histogram pixel distribution of the encrypted image is uniform. This effectively improves the security and robustness of the communication system.