# A Hybrid-Cryptography Engine for Securing Intra-Vehicle Communications
## 2 Intra-Vehicle Security
### Challenges and Security Measures in Intra-Vehicle Networks  
**Intra-Vehicle Communication Bus Security**  
One of the most critical aspects is represented by the communication buses adopted for intra-vehicle communications. In this field, while several solutions and architectures are competing, Figure 1 summarizes an overview of the intra-vehicle communication technologies and protocols released in the recent years. As depicted, there is an increased proliferation of the Automotive Ethernet standards: more consolidated protocols (e.g., LIN, CAN and Flexray), while being still actively adopted, exhibit a slower release cycle. In fact, manufacturers tend to adopt heterogeneous solutions driven by the requirements and capabilities of ECUs. This often results in a complex hierarchical multi-level network that incorporates multiple technologies (e.g., the example scenario shown in Figure 2) wherein securing communications is a non-trivial task. Among those communication technologies, the most commonly adopted are:  
* CAN bus (CAN-FD, CAN-XL);
* LIN bus;
* Flexray;
* Automotive Ethernet. Traditionally, the _Controller Area Network_ (CAN) bus and its evolutions are still a def-facto standard for intra-vehicle communications. Nowadays, CAN bus adoption is often limited to near-ECU or subsystem-local communications, while other technologies are adopted when configuring a vehicle communication backbone (e.g., automotive Ethernet). Given the importance of the CAN bus in intra-vehicle communications, securing the CAN bus is of paramount relevance. In [12] the authors provides a review of the main footholds a malicious actor can exploit to attack the CAN bus. On the other side, in [13], the authors provide an overview on the vulnerabilities, attacks, and possible cryptography-based  
Automotive Ethernet is an alternative standard for intra-vehicle communications. Its main advantage is the compatibility with communication (and security) solutions and protocols typically available in computer networks. Alongside its advantages, however, Automotive Ethernet inherits the long list of security weaknesses, vulnerabilities, and attacks that afflicted and afflict Ethernet-based solutions. A security perspective of Automotive Ethernet, limited to the intra-vehicle scenario, can be found in [24]: in this case the authors propose some remarks on Automotive Ethernet when adopted in intra-vehicle communications. In comparison with the reported bus-specific security measures, in the present work we propose a bus-agnostic security solution, which can be adopted without imposing requirements on the underlying communication bus. Our solution adopts a layered architecture that abstracts the communication bus and make the cryptographic operations independent from the protocol and technology used for communications. This abstraction, however, requires an explicit inclusion of bus-specific software drivers/wrappers and hardware support for the selected communication buses. The latter feature defines the set of adaptations to be carried out whenever an upgrade of the communication buses occurs. **Network Traffic filtering**  
One core security measure is the automatic analysis and filtering of the data and control messages exchanged by the nodes of the intra-vehicle network. Well-known tools such as firewalls and techniques such as (deep) packet inspection and flow analysis are adopted as well in intra-vehicle networks. For example, in [25], the authors describe the adoption of well-known firewalling and packet analysis techniques for intra-vehicle networks: from a security perspective it is suggested to use a real-time Operating System and HSMs to provide fast and lightweight implementation of the core cryptographic primitives to secure and authenticate traffic. **Intrusion Detection**  
Blocking and filtering communications via firewalls may not be sufficient to avoid malicious and dangerous traffic flows reaching the vehicle ECUs.