# Secure and Lightweight Cloud-Assisted Video Reporting Protocol over 5G-Enabled Vehicular Networks
## 6 Performance Evaluation
### Security  
The security achievements of the proposed protocol are as follows:  
* _Authentication_: The authentication for every \(v_{i}\) requesting a service file is provided by the certificateless signature scheme on message \(RReq=\{alias_{i},K,ts\}\) with \(C_{1}=Enc_{PK_{DMV_{i}}}\{RReq,pk_{v_{i}},\delta_{i}\}\). No malicious user can falsify a valid signature based on the hardness of DL problem. Otherwise the verifier could check the validity of the message by running CLS.Verify(\(m\), \(id\), \(pk_{id}\), \(\sigma\)) to check if \(r\cdot(R+h_{2}\cdot P)\stackrel{{?}}{{=}}P_{id}+R_{id}+(h_{1} \cdot P_{pub})\). Thus, the authentication is guaranteed for the proposed protocol.
* _Authorization_: Every vehicle has to get a periodic credential before it can participate in video reporting. \(v_{i}\) sends \(C_{1}=Enc_{PK_{DMV_{k}}}\{RReq,pk_{v_{i}},\delta_{i}\}\) to the \(DMV_{k}\) to request a credential. After a valid verification, \(DMV_{k}\) sends \(C_{1}=Enc_{K}(R-cred)\) where \(R-cred=\langle alias_{i},exp,KN,\omega_{v_{i}}\rangle\) as \(v_{i}\)'s credential which allows the \(v_{i}\) to participate in video reporting.
* _Identity privacy preservation_: It is hard for an attacker to get a real identity of a vehicle within our proposed protocol. In the registration stage of the vehicle provided by TA, every vehicle \(v_{i}\) is provided with a pseudo-identity \(alias_{v_{i}}\). Though the malicious user would get the credential request message \(RReq=\{alias_{i},K,ts\}\), the single plain identity of \(v_{i}\) which is available is its pseudo-identity \(alias_{v_{i}}\). In the rest of the protocol, the remaining available information concerning \(v_{i}\) is its pseudo-identity \(alias_{v_{i}}\). We confirm that our protocol achieves identity privacy preservation.
* Fine-grained access control: In the proposed protocol, the video file \(Vfile\) sent to \(v_{i}\) is encrypted under a set of attributes as \(SF_{j}\leftarrow\text{ABE.Encrypt}(Vfile_{j},\omega_{j},\mathit{labe.params})\). The file is sent encrypted under the public key of \(RSC_{j}.RSC_{j}\) only checks if \(KN\in List_{KN}\); this will save the \(RSCs\) from availing bogus files to \(DV\)s. \(RSC_{j}\) can not recover the file. Even for \(DV\)s, unless a \(DV_{j}\) possessesthe required secret shares \(D_{leaf_{l}}=q_{leaf_{l}}(0)\cdot t_{i}^{-1}\), it cannot reconstruct the root node \(R\) to be able to get the secret \(q_{root}(0)\cdot k\cdot P=s\cdot k\cdot P\). Throughout the decryption stage based on the root or child node, except \(DV_{j}\) has the obligatory secret shares, the decryption procedure returns \(\bot\). Consequently, even the entities (vehicles)that share a certain number of attributes can not conspire (collude) together to recuperate the secret that will achieves the decryption of the video file.
* Non-repudiation: A vehicle can not deny of participating in video reporting because the receiving \(RSC_{j}\) keeps \(v_{i}\)'s pseudo identity and its anonymous keyword \(KN\) contained in the credential \(R-cred=\langlealias_{i},exp,KN,\omega_{v_{i}}\rangle\).
* Traceability: Even though it is hard for an attacker to know the real identity of a vehicle, TA has the capability of revealing the vehicle's real identity in case of disputes. TA makes a search to find which real identity corresponds to any given or reported \(alias_{v_{i}}\). We conclude that the proposed protocol satisfies the traceability property.