# Secure and Efficient Authentication Scheme in IoT Environments
## 5 Evaluation
### Comparison by Functional Requirement  
This subsection compares the proposed scheme with those of the existing schemes by satisfying the following crucial functionality requirements: \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Schemes**} & \multirow{2}{*}{**Computation Cost (\(ms\))**} & \multirow{2}{*}{**\# of Messages**} & \multicolumn{2}{c}{**Communication Cost**} & \multirow{2}{*}{**Storage Cost (Bit)**} \\  & & & & **(Bit)** \\ \hline [PERSON] et al. [16] & \(36T_{h}=1.404\) & 4 & 3072 & 640 \\ [PERSON] et al. [17] & \(34T_{h}=1.326\) & 4 & 2176 & 384 \\ [PERSON] et al. [18] & \(9T_{h}+7T_{cm}=1.121\) & 5 & 1792 & 384 \\ [PERSON] et al. [20] & \(11T_{h}+13T_{cm}=1.859\) & 4 & 2176 & 640 \\ [PERSON] et al. [21] & \(1T_{pair}+6T_{cap}+6T_{h}=3.284\) & 3 & 1408 & 768 \\ [PERSON] et al. [22] & \(11T_{h}+9T_{cm}=1.419\) & 3 & 1408 & 640 \\ [PERSON] et al. [23] & \(28T_{h}=1.311\) & 10 & 5376 & 512 \\ [PERSON] et al. [24] & \(21T_{h}+5T_{s}=4.249\) & 4 & 2304 & 768 \\ [PERSON] et al. [25] & \(34T_{h}=1.326\) & 3 & 1664 & 640 \\ Proposed & \(7T_{h}+6T_{cm}=0.933\) & 3 & 1408 & 384 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of computation, communication, and storage costs. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Schemes**} & \multirow{2}{*}{**Mutual**} & \multirow{2}{*}{**Friendly Password**} & \multirow{2}{*}{**Session-Key**} & \multirow{2}{*}{**Secured Password**} \\  & & **Selection and Its Security** & **Agreement** & **Update** \\ \hline [PERSON] et al. [16] & Supported & Supported & Supported & Supported \\ [PERSON] et al. [17] & Supported & Supported & Supported \\ [PERSON] et al. [18] & Supported & n/a & Supported & n/a \\ [PERSON] et al. [20] & Supported & n/a & Supported & n/a \\ [PERSON] et al. [21] & Supported & Supported & Supported & Supported \\ [PERSON] et al. [22] & Supported & Supported & Supported & Supported \\ [PERSON] et al. [23] & Supported & Supported & Supported & n/a \\ [PERSON] et al. [24] & Supported & Supported & Supported & Supported \\ [PERSON] et al. [25] & Supported & n/a & Supported & n/a \\ Proposed & Supported & Supported & Supported & Supported \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of functional requirements. Mutual authentication: The proposed scheme provides mutual authentication between embedded devices (\(ED_{i}\)) and server (\(TS\)) by using a three-way challenge-response handshake technique. The \(TS\) validates \(ED_{i}\) by checking whether \(Y_{i}^{\prime}\)(i.e., \(h(X_{i}.CK))=\)\(\mathcal{Y}_{i}\) and \(C_{i}^{\prime}\)(i.e., \(h(Y_{i}\|A))=\)\(\mathcal{T}_{C_{i}}\), while \(ED_{i}\) validates \(S\) by verifying whether \(Y_{i}^{\prime}\)(i.e., \(h(X_{j}.A))=\)\(\mathcal{T}_{Yj}\). It is impossible to compute \(Y_{j}^{\prime}\) without knowing \(CK^{\prime}\) and \(I_{i}\) as both \(CK^{\prime}\) and \(I_{i}\) are completely secure due to the tamper-proof nature of the device [43]. Furthermore, in a server, the security of \(CK\) depends upon the factors R and E\({}_{t}\). This factor (i.e., \(R\), \(A\) and \(E_{t}\)) security is protected by a secret server key (s) and a secret identity. This parameter (i.e., \(s\) and \(ID_{TS}\)) security is preserved in a server key (\(E_{ks}=s.ID_{TS}.G\)) by the concept of ECDLP and CDHP. For the above-mentioned reasons, the attacker cannot compute factors \(h((Y_{i}\|A))\) and \(h(X_{i}.CK)\) without knowing \(A\) and \(CK\). Thus, only \(ED_{i}\) and \(TS\) can mutually authenticate each other. The result shown in the Proverif tool in Section 4.3 verifies the mutual authentication confirmation. Therefore, the proposed scheme achieves mutual authentication. * Confidentiality (or friendly password selection and its security): In the proposed scheme, for easy remembering, the client can pick a simple password \(psw_{i}\), which might be of low or high intensity [41]. This password is stored in the password-generator format (i.e., \(P_{ke}=psw_{i}.G\)).