# How Does C-V2X Help Autonomous Driving to Avoid Accidents?
## 3 Key Technology for C-V2X VRUCW
### Security Support  
Even though the essential security and privacy aspects of C-V2X specified by 3 GPP are introduced in [27], there is no security details definition in V2X application layer in Rel-16 specification [28], i.e., confidentiality and integrity protection for group communication. Therefore, prior to marketization of C-V2X technology services deployment, government must ensure the security and privacy of C-V2X Sidelink transmission in a reliable and trust level, and protect C-V2X Sidelink transmission from hacker's attacking, e.g., Jamming, Eavesdropping and others as introduced in [29; 30; 31]. In this paper, we neither address complicated 5G core network security policy in C-V2X V2N mode where authentication is stated as the procedure of verifying the user before providing access to the system and only authorized user can have access rights to the network, nor involve third party Certificate Authority (CA) which requires government by using unified regulations to drive authority agency, nor provide hardware security model (HSM) which is easy to trigger higher cost investment based on available hardware capability in current market. Instead, our approach does not require any additional infrastructure, we design a symmetric software encryption function for C-V2X Sidelink transmission which is suitable for early C-V2X technology market. An original system architecture of security support for C-V2X VRUCW service is firstly proposed. In Figure 9, the entire design for security support of C-V2X Sidelink transmission is consists of two resident modes (User mode and Kernel mode) and a key profile management tool. The security process is proceeded between the network layer and application layer of C-V2X RSU/OBU program simultaneously. C-V2X Security Proxy and C-V2X APP Proxy use Inter-Process Communication method. When C-V2X APP. proxy detects that security function is turn on, the upcoming packages will be sent to C-V2X security proxy by security network interface for software symmetric encryption algorithms process. Advanced Encryption Standard-Electronic Codebook (AES-ECB) mode as our selection is enough to provide a secure cipher procedure for encrypting and decrypting some sensitive string values in C-V2X Sidelink transmission. Key file is managed by key profile generation tool. Symmetric encryption key has been copied into both RSU and OBU devices manually in advance. Symmetric means ciphers use the same key for encrypting and decrypting, so the sender and the receiver must both know and use the same secret key. Figure 8: Vulnerable Road User Category. According to message header definition in Figure 10, security packet messages are encapsulated and de-encapsulated as designed. In Figure 11, before wireless device communication with security support, we first generate key profile by using our key file management tool, then input same key files into C-V2X RSU and OBU in both Sending/Receiving thread, active or inactive security function in both devices keeps same. During RSU sending data, its C-V2X security proxy is responsible for monitoring and reading the status of C-V2X application proxy, if encrypt type \"0 \(\times\) 01\" is gotten, data will be sent to security proxy for encryption progress. Another communication side, OBU is listening on receiving data, when encrypt type \"0 \(\times\) 01\" encryption is detected, it will proceed decryption procedure then send plain-text to application layer of device for executing C-V2X services such as our VRUCW solution for example. Without same key profile or encrypt type, RSU and OBU cannot talk each other so as to achieve a guarantee of C-V2X Sidelink transmission security in the field experiment. We admit that AES-ECB mode in our solution has some known weakness, which there is still possibility that an attacker breaks into our database and steals our data after their many planned entries. But as proof of concept as we emphasize, our target is to address a workable security support for C-V2X during the early stage deployments in some countries.