# A Blockchain-Assisted Security Protocol for Group Handover of MTC Devices in 5G Wireless Networks
## 7 Performance Evaluation
### Energy Consumption  
The security protocols that offer the highest level of security functionality while consuming the least amount of energy are always the preferred choice due to the limited battery life of mobile devices like MTCDs. To evaluate the energy consumption of MTCDs, two factors should be considered including the energy required for data transmission and the energy consumed for the execution of the cryptographic functions. For the energy used for data transmission, the evaluation of energy consumption follows the data transmission  
Figure 9: Comparison of the authentication cost for 30 MTCDs with unknown attacks.  
power model described in [28]. The calculation of the transmission energy cost for the uplink and downlink is as follows:  
\[E_{ul}=(\alpha_{u}t_{udr}+\beta)\cdot t_{ul} \tag{39}\]  
\[E_{dl}=(\alpha_{d}t_{ddr}+\beta)\cdot t_{dl} \tag{40}\]  
where \(\alpha_{u}=438.39\) mW/Mbps, \(\alpha_{d}=51.97\) mW/Mbps, \(\beta=1288.04\) mW, \(t_{udr}=25\) Mbps, and \(t_{ddr}=50\) Mbps. \(t_{udr}\) represents the uplink throughput, \(t_{ddr}\) represents the downlink throughput, \(t_{ul}\) is the transmission time for uplink, and \(t_{dl}\) is the transmission time for downlink.  
For the energy used for performing cryptographic functions, the way of approximation of energy cost in [30] is adopted. All experiments were conducted using a battery-powered Compaq iPAQ H3670 PDA, which is equipped with an Intel SA-1110 StrongARM processor running at 206 MHz, 64 MB RAM, and 16 MB FlashROM for evaluation. The energy cost of a single AES encryption or decryption operation is \(7.87+1.21\) uJ, where \(b\) is the number of bytes in the plaintext. The energy cost per byte for a SHA-1 hash operation \(E_{H}\) is 0.76 uJ. Considering that the energy cost for generating an ECDH public key is 276.7 mJ and for deriving an ECDH public key is 163.5 mJ, the energy consumption for a single scalar multiplication operation \(E_{PM}\) is approximately estimated to be 220.1 mJ, and the energy cost for a single RSA operation \(E_{RV}\) is 832.6 mJ. The energy consumption of using cryptographic primitives is derived based on the cryptographic operations used in the protocol, leading to a theoretical energy cost.  
Figure 10 illustrates the relationship between the energy consumption during handover authentication and the number of MTCDs in a group. It is clearly visible from the figure that, compared to the NASS protocol, the energy consumption of BSPGH is lower and more efficient as the number of MTCDs increases. Additionally, the energy consumption of the 5G and PPHAP protocols is lower than our protocol. However, the 5G standard protocol has security issues and is susceptible to different malicious attacks, while the PPHAP protocol is also vulnerable to security threats like DDoS attacks. On the other hand, the BSPGH protocol can significantly enhance network security, albeit at a slightly higher cost compared to other protocols. It can also facilitate group handover authentication for a large number of users simultaneously. Therefore, the BSPGH protocol exhibits a better performance in terms of both security and efficiency.  
Figure 10: Comparison of the energy consumption.