## 9 Efficiency Analysis
### Efficiency Comparison of Several Communication Methods  
In order to test the transmission efficiency of the MHC method, the experiment compared the efficiency of the network layer using the traditional IP protocol, the AH protocol, and the ESP protocol of IPSec with the method. At the same time, the communication method of IP protocol, which is signed and authenticated packet by packet to ensure data non-repudiation, is compared with the transmission efficiency of several other communication methods. The experiment set up five groups of test subjects. The transport layer of each group of experiments uses the TCP protocol. The network layer uses the IP protocol, the IP protocol with packet-by-packet signature and authentication, the AH protocol, the ESP protocol of IPSec, and the MHC method. We recorded the average number of messages transmitted by five groups of subjects in 2 min, 5 min, 10 min, 30 min, and 60 min, and the number of those in each group was the average of ten tests. The throughout capacity is then calculated based on the average amount of data transferred per group. Finally, the estimated throughout capacity is used as the standard to measure the transmission efficiency, and the efficiency of several groups of experimental objects is compared. The relevant information of the experiment is shown in Table 2.  
Among them, the AH protocol test group uses the transmission mode, and the identity authentication method uses certificate authentication. The life cycle of the first stage negotiation is 86,400 s, and the life cycle of the second stage negotiation is 120 s. AHH represents the AH protocol header, with a length of about 24 B; The ESP protocol test group also uses the transmission mode, and the identity authentication method uses certificate authentication. The life cycles of the first and second stages of negotiation are 86,400 s and 120 s, respectively. It is set to only verify the integrity of the message. ESP represents the ESP protocol header, with a length of about 24 B; The MHC method test group set its signature interval to 1000, and the other experimental settings are consistent with those in 6.2. The experimental test results are shown in Table 3.  
The AH protocol experimental group uses the transmission mode, and the identity authentication method uses certificate authentication. The life cycle of the first-phase negotiation is 86,400 s, and the life cycle of the second-phase negotiation is 120 s. The ESP protocol experimental group maintains the same settings as the AH protocol experimental group, and at the same time, it only performs integrity verification on messages. The MHC method experimental group set the signature interval to 1000. MTU in Table 2 is the maximum transmission unit, and its length is 1500 B. TCPH is the TCP header, whose length is 20 B, while IPH is the IP header, the length is 20 B. MHCH is the MHC header, including the sequence number length of 4 B, the remaining fields of about 4 B, and the node value of the message hash chain length of 32 B, with a total length of 40 B. Finally, AHH is the AH protocol header with about 24 B, and ESPH is the ESP protocol header with about 24 B. The experimental results are shown in Table 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Serial** & **Transport Layer** & **Communication Mode** & **Payload Length of Each Message** \\
**Number** & **Protocol** & & \\ \hline
1 & TCP protocol & IP protocol & 1460 B \\
2 & TCP protocol & Packet by packet signed IP protocol & 1372 B \\
3 & TCP protocol & AH protocol & MTU-TCPH-IPH-AHH = 1436 B \\
4 & TCP protocol & ESP protocol & MTU-TCPH-IPH-ESPH = 1436 B \\
5 & TCP protocol & MHC method (signature interval 1000) & About 1420 B without signature and about 1332 B with signature \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Information about test contents. Figure 4 shows the comparison of the experimental results of the five groups of experiments.