## 4 System Methodology
### Proposed System Workflow
#### 4.2.2 Phase 2: Registration and Key Generation
In the traditional cryptography-based security systems, these responsibilities are performed by a trusted assumed third party or CA, which was replaced in the proposed work by blockchain with the integration of smart contract. Therefore, the proposed solution can be outlined as a trusted third party-free solution. As shown in Figures 7 and 8, the proposed scheme's total time and communication cost is lower than that of the others. [PERSON] et al. [8], [PERSON] et al. [9], [PERSON] et al. [12], and [PERSON] et al. [13] proposed cryptography-based AMI security models required a time cost of 55.98 ms, 158.06 ms, 32.16 ms, and 266 ms, respectively, and communication cost of 1376 bits, 2240 bits, 6144 bits, 1538 bits, and 1376 bits, respectively. In contrast, our proposed blockchain-based scheme incurs the least time of 20.59 ms and a communication cost of 1346 bits. Figure 7: Comparative performance analysis between proposed and existing works in terms of time cost analysis [8; 9; 12; 13]. After the progression of blockchain, some other works in smart metering security have designed only theoretical frameworks under some informal security features analysis. [PERSON] et al. [19] and [PERSON] et al. [20] both designed TTP-free smart meter security schemes that include informal security analysis but their implementation, required time, or cost analysis is unknown. Table 4 compares the informal security features between proposed and existing works. The security protocols designed by [PERSON] et al. [19] and [PERSON] et al. [20] do not ensure PFS feature, therefore the systems are vulnerable to session key replacement attack and neglect the auto-refresh of the key. Moreover, the consensus algorithms implemented by these security protocols do not have BFT property, and eventually it leads to 51% attack in their proposed blockchain platform. With comparison to these studies, our proposed BC-AMI scheme ensures PFS and BFT security properties to prevent key replacement and 51% attacks, respectively. ## 6 Conclusions

In this work, we address the problem of conventional TTP-based cryptography AMI security models that eventually lead to single point of failure with an increasing amount of network overhead. We deprecate the role of traditional TTP with smart contract functionalities based on blockchain implemented on the HLF platform. This platform implements PBFT as their ordering service to avoid 51% attacks and ensures network fault tolerance. According to the informal security discussion, the proposed scheme has perfect forward secrecy, message integrity, authentication, signature correctness properties, resistance to key replacement, MITM, impersonation, and replay attacks. Furthermore, the proposed scheme takes the least time and communication cost among the compared schemes. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Study** & **F1** & **F2** & **F3** & **F4** & **F5** & **F6** & **F7** & **F8** & **F9** & **F10** \\ \hline \
\begin{tabular}{c} [19] \\ [20] \\ \end{tabular} & \(\times\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) \\
\begin{tabular}{c} Proposed \\ \end{tabular} & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison based on informal security features between proposed and existing works. Figure 8: Comparative performance analysis between proposed and existing works in terms of communication cost analysis [8; 9; 12; 13]. The proposed BC-AMI security scheme was designed to concentrate on permissioned consortium blockchain platforms. Since the consortium blockchain implementation has not yet been appropriately documented, we implemented the proposed scheme using a private HLF blockchain platform. The consortium implemented blockchain platform is currently in development. Thus, the future scope of this research work lies in the proper implementation of consortium blockchain to analyze the security performance.