# A Survey of Internet of Things (IoT) Authentication Schemes +
## 7 Conclusions
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**Ref\#** & **IoT Layer** &
\begin{tabular}{c} **Identity Context** \\ **Credentials** \\ \end{tabular} & **Token Based?** & **Proc.** & **Arch.** & **HW.** & **Strength(+)/Weakness(–)** \\ \hline
[141] & A & \
\begin{tabular}{c} Encryption: registered user \\ with AES and non-registered \\ users using Diffie-Hellman \\ \end{tabular} & x (username password) & + & 1 & C/F & I &
\begin{tabular}{c} +Two separate servers for storing cryptography and authentication data, \\ +Resistance to brute force, timing, and \\ MITM \\ \end{tabular} \\ \hline
[82] & P & \
\begin{tabular}{c} Encryption/Symmetric using \\ AES \\ \end{tabular} & ✓ & 2 & C/H & I &
\begin{tabular}{c} +Resistance to split attacks (i.e., swapping \\ tags, separating tag from product, etc.) \\ \(-\)No analysis is done for location privacy. \\ \end{tabular} \\ \hline
[162] & A & \
\begin{tabular}{c} No Encryption/Hash \\ \end{tabular} & ✓ & 1 & D/F & I &
\begin{tabular}{c} +Resistance to MITM, replay, DoS, and \\ Eavesdropping attacks. \\ \(-\)Storage cost is not efficient \\ \end{tabular} \\ \hline
[140] & A & \begin{tabular}{c} Context /multiple \\ credentials using physical \\ context \\ \end{tabular} & x (User name +  password) & + & \
\begin{tabular}{c} Multiple \\ authentication \\ \end{tabular} & D/H & I &
\begin{tabular}{c} +Resistance to replay attack \\ \(-\)DoS attack is not considered \\ \end{tabular} \\ \hline
[142] & A & \
\begin{tabular}{c} No Encryption/Hash 256 \\ bits + context bio-metric \\ \end{tabular} & ✓ (User Identity) & 2 & D/F & E &
\begin{tabular}{c} +Second-tier authentication is done at client side. \\ \(+\)Resistance to attacks from inside the system. \\ \(-\)No ability to change credentials in both \\ the tiers. \\ \end{tabular} \\ \hline
[121] & A & \
\begin{tabular}{c} Encryption/Asymmetric \\ using ECC \\ \end{tabular} & ✓ (UserId) & 2 & D/F & I &
\begin{tabular}{c} +Resistance to MITM and DoS attacks. \\ \(-\)User must be authenticated many times in Multi-server environment. \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Ref\#** & **IoT Layer** &
\begin{tabular}{c} **Identity Context** \\ **Credentials** \\ \end{tabular} & **Token Based?** & **Proc.** & **Arch.** & **HW.** & **Strength(+)/Weakness(–)** \\ \hline
[79] & A & \
\begin{tabular}{c} Encryption /RSA + Hash \\ SHA or MD5 \\ \end{tabular} & x & 2 & C/H & I &
\begin{tabular}{c} + Filtering of the messages at gateway \\ + Privacy preservation is considered \\ +Resistance to Brute force, DoS, and Replay \\ -DDoS is not considered. \\ \end{tabular} \\ \hline
[77] & A + N & Encryption /RSA + AES & x & 2 & D/ F & I &
\begin{tabular}{c} +Resistance to Modification, Replay, and \\ Message analysis attacks \\ \end{tabular} \\ \hline
[111] & A + N & \
\begin{tabular}{c} Encryption/Symmetric + \\ Hashing \\ \end{tabular} & ✓+ x & 2 & C/F & I &
\begin{tabular}{c} +Resistance to Replay, Impersonation, \\ Spooring, and Gateway attacks. \\ -Blackhole and Wormhole attacks are not studied \\ \end{tabular} \\ \hline
[135] & A + N + P & Encryption/Symmetric & ✓(Identity) & 2 & C/F & I &
\begin{tabular}{c} +Resistance to MITM and DoS attack \\ -Identity and Location privacy is not considered \\ \end{tabular} \\ \hline
[130] & A + N + P & \
\begin{tabular}{c} Encryption/Asymmetric \\ using ECC \\ \end{tabular} & ✓(Identity) & 3 & C/F & I &
\begin{tabular}{c} +Resistance to redirection, malicious,Dos, \\ and MITM attacks. \\ -Location and Identity privacy is not analyzed and can not authenticate group of machines at the same time \\ \end{tabular} \\ \hline
[129] & N + P & Encryption/Asymmetric & ✓(Identity) & 2 & C/F & I &
\begin{tabular}{c} +Location privacy is analyzed \\ +Low communication and computational cost. \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._