# An Enhanced Lightweight IoT-based Authentication Scheme in Cloud Computing Circumstances
## 4 Security Analysis and Performance Evaluation
### Communication-Cost Comparison  
In this sub-section, we compare the communication-cost of our scheme with [PERSON] et al.'s scheme, [PERSON] et al.'s scheme and [PERSON] et al.'s scheme in terms of message length. For conventional comparison, we assume two bit length cases:  
* Case 1: any identity, password, pseudo-identity, timestamp, random nonce, and hash output are 128 bits.
* Case 2: any identity, password, pseudo-identity, timestamp, random nonce, and hash output are 256 bits.
* The block length of the symmetric encryption is 128 bits.  
Table 5 summarizes the message length by each entity during the scheme.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**[PERSON] et al.**} & \multicolumn{4}{c}{**[PERSON] et al.**} & \multicolumn{4}{c}{**[PERSON] et al.**} & \multicolumn{4}{c}{**Our Scheme**} \\ \hline  & & **Length** & **Case 1** & **Case 2** & **Length** & **Case 1** & **Case 2** & **Length** & **Case 1** & **Case 2** & **Length** & **Case 1** & **Case 2** \\ \hline \multirow{4}{*}{R} & \(U_{i}\) & 3 & 384 & 768 & 2 & 256 & 512 & 2 & 256 & 512 & 2 & 256 & 512 \\ \cline{2-11}  & \(S_{j}\) & 2 & 256 & 512 & 2 & 256 & 512 & 2 & 256 & 512 & 2 & 256 & 512 \\ \cline{2-11}  & CS & 2 & 256 & 512 & 3 & 384 & 768 & 6 & 768 & 1536 & 4 & 512 & 1024 \\ \cline{2-11}  & ST & & 896 & 1792 & & 896 & 1792 & & 1280 & 2560 & & 1024 & 2048 \\ \hline \multirow{4}{*}{L} & \(U_{i}\) & 6 & 768 & 1536 & 5 & 640 & 1280 & 5 & 640 & 1280 & 4 & 512 & 1024 \\ \cline{2-11}  & \(S_{j}\) & 11 & 1408 & 2816 & 9 & 1152 & 2304 & 10 & 1280 & 2560 & 9 & 1152 & 2304 \\ \cline{2-11}  & CS & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ \cline{2-11}  & ST & & 2176 & 4352 & & 1792 & 3584 & & 1920 & 3840 & & 1664 & 3328 \\ \hline \multirow{4}{*}{A} & \(U_{i}\) & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 2 & 256 & 512 \\ \cline{2-11}  & \(S_{j}\) & 2 & 256 & 512 & 2 & 256 & 512 & 3 & 384 & 768 & 5 & 640 & 1280 \\ \cline{1-1} \cline{2-11}  & CS & 4 & 512 & 1024 & 4 & 512 & 1024 & 6 & 768 & 1536 & 6 & 768 & 1536 \\ \cline{1-1} \cline{2-11}  & ST & & 768 & 1536 & & 768 & 1536 & & 1152 & 2304 & & 1664 & 3328 \\ \hline \multirow{4}{*}{L} & T & 30 & 3840 & 7680 & 27 & 3456 & 6912 & 34 & 4352 & 8704 & 34 & 4352 & 8704 \\ \cline{1-1} \cline{2-11}  & \multicolumn{4}{c}{*R = Registration phase, L = Login phase, A = Authentication phase, ST = Subttal, T = Total.} \\ \hline \hline \end{tabular}
\end{table}
Table 5: Communication cost comparison.  
Figure 7: Computational-cost comparison by participant.  
From Table 5, we see very clearly that our scheme requires the same message length as Zhou et al.'s scheme, 4352 bits or 8704 bits. However, our scheme provides mutual authentication and evidence of connection attempt, which requires more information to share among participants. If we pay attention phase by phase, our scheme requires less message length during the registration phase than Zhou et al.'s scheme, making our proposal more efficient. In fact, our proposal requires less message length in the login phase than previous works, making it more efficient. After achieving the performance evaluation of the proposed scheme, it is possible to confirm that the proposal has good performance.