# Secure and Lightweight Cloud-Assisted Video Reporting Protocol over 5G-Enabled Vehicular Networks
## 6 Performance Evaluation
### Cost Comparison
#### 6.2.2 Overall Cost Including Communication Cost  
Note that TA uses secure symmetric encryption/decryption algorithm. For fairness in comparison, we adopt AES/CBC (256-bit key) with a processing speed of 65 MB/s. We also consider the size of the video ranging from 2 to 8 Gigabytes. We use SHA-512 hash function with a processing speed of 231 MB/s. The connection speed for the 5G-enabled vehicular network is set to 1.2 Gb/s and vehicle's velocity to 100 km/h [53]. We also use CP-ABE toolkit [54] along with MIRACL [55] library to benchmark the performance of attribute-based encryption. We set the attribution number to 4 by following the reference [18]. The overall operation involved for signing and verifying is illustrated in Table 3. As being described in Section 5.4, \(v_{i}\) computes \(W_{i}=k\cdot P_{i}\) and \(q_{leaf_{l}}(0)\cdot t_{i}^{-1}\) ; which equals to \((d+1)T_{mul}\) where \(d\) is the number of attributes based on the access structure. Furthermore, \(v_{i}\) sends the file encrypted under the public of \(RSC_{j}\) which equals to \(T_{as\_enc}\). \(RSC_{j}\) only decrypts the file and check the validity of the \(KN\) which was earlier provided within the vehicle credential. In Figure 3, we show the time overhead for encrypting and signing the files recorded by the vehicles' OBUs.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \(Notation\) & **Operations** & **Time (ms)** \\ \hline \(T_{pair}\) & Bilinear pairing & 4.5 \\ \(T_{mal}\) & Point scalar multiplication & 0.6 \\ \(T_{as\_enc}\) & Asymmetric encryption & 1.17 \\ \(T_{as\_dec}\) & Asymmetric decryption & 0.61 \\ \(T_{s\_enc}\) & Symmetric encryption & 0.51 \\ \(T_{s\_dec}\) & Symmetric decryption & 0.55 \\ \(T_{h}\) & hash function & 0.0001 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Measurement of cryptographic operations.  
To recover the video file, \(DV_{i}\) decrypts the file in \(T_{as-dec}\) and checks if \(r\cdot(R+h_{2}\cdot P)\stackrel{{?}}{{=}}P_{id}+R_{id}+(h_{1}\ \cdot P_{pub})\) for signature verification in \(2T_{mul}\). \(DV_{j}\) computes \(q_{leaf_{1}}(0)\cdot k\cdot P\) in \(dT_{mul}\). On the other hand, the protocol in [18] requires \(T_{pair}+T_{mul}\) to perform _public key encryption with key search_[56]; \((d+1)T_{mul}+(d+1)T_{pair}\) for attribute-based encryption and \(T_{mul}\) for signature generation. In order to recover the video file, the designated vehicle requires \(3T_{pair}+4T_{mul}\) for certificate and signature verification and \(4T_{pair}\) for attribute-based decryption. The total overhead which comprises the required time to encrypt, sign, transmit, verify and decrypt the reported file is shown in Figure 4. It is predicated that the connection speed for the 5G-enabled vehicles will be higher than \(1.2\) GB/s up to \(1\) Tb/s which has been already achieved for stationary wireless connection [57]. In Figure 5, we show the overall time overhead with different 5G connection speeds for a 2 GB video file. As shown in Figure 4, the time for the vehicle's OBU to encrypt, sign and decrypt the recorded file in the proposed protocol is also less than the Eiza-Ni-Shi protocol [18] by 50%. These observations show that the proposed protocol offers the possibility to the vehicles that witnessed abnormal events such as road's accidents to report the scene to the designated entities for a timely response.