## 9 Efficiency Analysis
### Comparison and Analysis of Security Properties of Several Existing Schemes  
In order to illustrate the security properties and efficiency of this scheme, this paper compares the chain network transmission mode using the MHC protocol at the network layer with the transmission mode using the IP protocol, IPSec protocol, and other existing schemes at the network layer. The differences in several security properties are shown in Table 5.  
Figure 4: Comparison of average transmission efficiency of five communication methods. The IP protocol without a security mechanism has the highest transmission efficiency, but it does not have any security properties, which is easy to cause network attacks. After the IP protocol is signed and authenticated packet by packet, although the security of its transmission is improved, it also dramatically reduces the transmission efficiency. Both the AH protocol and ESP protocol of IPSec can ensure the integrity, non-tampering, and certain reliability of the messages, and the ESP protocol can also ensure the confidentiality of the messages. However, these two protocols cannot guarantee the non-repudiation of messages during the transmission process and are vulnerable to denial attacks by both parties. The rest of the schemes improve application-layer communication methods or use different hash chain structures and signature methods to improve security. Although the star-shaped and tree-shaped hash chain structure in the [11] can ensure that a signature can verify the child nodes under each tree, it cannot process packet loss data. The hash chain structure in the [12] improves the transmission efficiency, but it still cannot adapt to the network with the possibility of packet loss. The method in [13] caches the data, calculates its hash value, and then places the hash value in the message to be sent before verifying the later content with the previous content. This method needs to know the content of the entire transmission before transmission, which reduces the transmission efficiency and does not have security mechanisms such as reliability and confidentiality. The improved butterfly hash chain proposed in [15] has a complex structure, resulting in low transmission efficiency. The method in [16] is improved for the Modbus/TCP protocol at the application layer. It guarantees the confidentiality of the protocol through symmetric encryption and digital signature and can resist replay attacks by using a synchronization mechanism and a one-way guarantee scheme of a hash function. However, it still signs and authenticates each packet, resulting in low transmission efficiency. The MHC method ensures the integrity and immutability of the transmitted message through the hash chain. It uses the chain signature technology to realize the batch signature and authentication of the message stream, significantly reducing the overhead of signature and authentication. According to the characteristics that the message hash chain needs to be calculated, we designs the packet loss retransmission and chain synchronization mechanism to ensure the protocol's reliability and synchronization. It has the security properties of traceability and confidentiality. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Schemes and Configurations**} & \multicolumn{5}{c}{**Length of Transmitted Data**} \\ \cline{2-6}  & **1 GB** & **5 GB** & **10 GB** & **50 GB** \\ \hline The MHC method/signature interval is 1000 & 68.76 s & 337.47 s & 678.31 s & 3374.16 s \\ AH protocol/SA phase II life cycle is 2 min & 70.68 s & 358.53 s & 712.34 s & 3568.89 s \\ AH protocol/SA phase II life cycle is 5 min & 70.75 s & 353.60 s & 704.51 s & 3530.46 s \\ AH protocol/SA phase II life cycle is 10 min & 70.03 s & 351.51 s & 701.97 s & 3514.27 s \\ AH protocol/SA phase II life cycle is 60 min & 70.00 s & 351.58 s & 698.37 s & 3510.16 s \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The experimental results of the transmission efficiency of the AH protocol communication method and the MHC method.