## 3 Vcc-Ssf
### Security Layer
\begin{table}
\begin{tabular}{c c} \hline \hline
**Terms** & **Definition** \\ \hline \(\text{Vs}/\text{V}_{\text{M}}\) & Stationary vehicle/Moving vehicle \\ CA/U/SP & Certificate Authority/User/Service Provider \\ RSU/ECU & Road Side Unit/Electronic Control Unit \\ Hash ( )/Shift ( ) & Hash Algorithm/Circular Shift Operation \\ \(\text{E}_{\text{x}}\)( )/\(\text{D}_{\text{y}}\)( ) & Encryption algorithm using x key/ \\ \(\text{Sig}_{\text{x}}\)( )/\(\text{Very}_{\text{y}}\)( ) & Signature algorithm using x key/ \\ \(\text{C}/\text{P}/\text{Cert}\) & Encrypted Message/Plain Text/Certificate \\ K\(\text{x\_prv}/\text{K}_{\text{x\_pub}}\) & Private Key of X/Public Key of X \\ PVID/RID & Pseudo Vehicular ID/Road Side Unit ID \\ R\({}_{\text{K}}\) & Random Values \\ DN/VN & Driver Number/Vehicle Number \\ X\_TS & Time Stamp Values of X \\ ET & Expiry Time of Certificate \\ AcNo & Number of Accesses \\ VC\_Int\_Info/VC\_Ext\_Info & Internal/External Information \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Definition of terms. If V_TS is 0, the vehicle is considered to be stationary. The stationary vehicle is marked as V\({}_{\text{S}}\), and the CA issues the certificate to Vs. The certificate includes the PVID and DN hash value, Time Stamp values of Certificate (C_TS), Expiry time of Certificate (ET), Road Side Unit ID (RID), and the Number of Accesses (AcNo). The C_TS is the time when the certificate is issued, and the ET is the expiration time of the certificate. The RID is the unique ID of the previous RSU, and by storing the IDs of RSU that vehicle has already passed, the system can verify the previous route. AcNo is the number of authentication attempts allowed. If there are more than AcNo access attempts, access and authentication to the corresponding vehicle is restricted. **Data Integrity:** Information encryption, along with integrity, should be provided. Hash functions and digital signatures are used to provide data integrity. * **Data integrity procedure:** Data integrity is provided for the Critical Info (_i.e._, Personal Information, Payment Information, Location, User Information, and User State), which is sensitive information used both inside and outside the vehicle. This procedure is as follows. Signing Vs, V\({}_{\text{M}}\)\(\rightarrow\) RSU: Sig Kv_pv (Hash(Critical Info)) \(\parallel\) P To maintain data integrity inside the vehicle, the user hashes the Critical Info and signs it with Kv_pv to generate a hash value. This is then sent to the RSU along with the original information P. Verifying RSU: H = Very Kv_pub (Hash(Critical Info)) The signed data is verified using Kv_pub, registered in the CA. In addition, the hash value is compared with hashing P. Hash value H is obtained after the mutual verification to check whether data integrity is guaranteed. **Encryption:** In VCC, sensitive information inside the vehicle, such as the private information and financial payment information as well as the ECU information that is collected using the On Board Unit (OBU) and On Board Equipment (OBE), should be protected through encryption. * **Encryption of the information inside the vehicle:** The Drive System, Braking System, Steering System, _etc._ inside the vehicle are controlled through the ECU. This information is frequently used inside the vehicle for service or function, and hence fast encryption is required. In this system, a symmetric key encryption method is used. Key generation is as follows: Generate Key = Shift(VN) \(\oplus\) R\({}_{\text{K}}\) The 128-bit unique number (VN) assigned by the manufacturer is used as the key for the symmetric key encryption. We perform a circular shift operation by seven bits on the VN, and eXclusive-OR the result with R\({}_{\text{K}}\), generated using a random number generator inside the vehicle, to generate the final key. Encrypt OBD, OBU \(\rightarrow\) U: C = Ekey (VC_Int_Info) VC_Int_Info (_i.e._, Speed, Fuel, Oil Pressure, Tire Condition, GPS, Temperature, _etc._) is displayed to the user inside the vehicle by the OBD.