## 8 Suggested Improvements
### Encryption, Authentication, and Access Control  
The ubiquitous integration of technologies such as BLE, WiFi, LTE, and the emerging 6G is able to enhance the reliability of automotive systems, but on the other side, it leads to an expansion of the attack surface. This expansion, as demonstrated in the threat assessment phase, mandates a comprehensive approach to secure these communication channels, thereby fortifying the ACN system against a diverse range of potential breaches. A very relevant branch of the literature is mainly focused on securing physical layers on heterogeneous networks [60, 61]. Continuing the discourse, major improvements in the reliability of the solutions analyzed may be the implementation of satellite communication leading to the research undergoing for the sixth generation of cellular networks [62]. While this technology augments communication coverage, it introduces the need for meticulous implementation of encryption and authentication protocols [63]. By bolstering the security of satellite-based data exchanges, the ACN system's resilience against adversarial exploitation is substantially elevated. The narrative then shifts towards the inseparable duo of the TCU and ECU. In both the analyzed architectures, we can identify them as two potential single points of failure, but as these two core components are crucial for the correct behavior of the module, some redundancy-based mechanisms and fail-safe protocols [64] need to be adopted. These safeguards ensure that even in the event of the TCU or ECU being compromised, the ACN system maintains its operational efficacy. An essential facet of fortifying the communication security of the ACNsystem, and more generally of automotive systems, resides in meticulous evaluation and streamlined elimination of redundant or unused features, such as Bluetooth connectivity when not essential. This pragmatic approach directly addresses the expansion of the attack surface, a concern paramount in contemporary vehicular cybersecurity. By meticulously examining and selectively deactivating features that are extraneous to the ACN system's core functionality, the potential vectors for malicious intrusion are substantially curtailed. This undertaking not only reduces the system's vulnerability but also enhances operational efficiency and elevates resource allocation. Moreover, this judicious removal of unnecessary features aligns seamlessly with the principle of minimalistic design, fostering a leaner, more secure vehicular architecture. Amidst these solutions, TPMs, as depicted in Figure 9, and more particularly HSMs emerge as potent tools [65, 66]. These specialized hardware devices provide a secure enclave for cryptographic operations, safeguarding sensitive cryptographic keys from potential compromise. While the introduction of HSMs needs a careful assessment of cost and potential performance implications, their integration aligns seamlessly with the ACN system's security imperatives. Tailored to address the diverse demands of the vehicular environment, HSMs can be optimally deployed across varying components based on their performance requirements and specific contexts. Low-performance HSMs find their niche within components like sensors, where resource constraints and real-time demands are of paramount concern. Designed for efficiency, these HSMs provide a lightweight cryptographic solution that ensures data integrity and privacy for these critical data collection nodes. These low-performance HSMs strike a balance between robust security and the exigencies of low-power sensors, safeguarding data even in the face of constrained resources. Transitioning to the TCU, the complexities of this central hub need a high-performance HSM. This level of HSM offers elevated processing power, capable of handling intricate cryptographic operations while maintaining real-time performance.