# A Survey of Internet of Things (IoT) Authentication Schemes +
## 7 Conclusions
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Ref\#** & **IoT Layer** & **Identity Context Credentials** & **Token Based?** & **Proc.** & **Arch.** & **HW.** & **Strength(\(\star\))/Weakness(\(-\))** \\ \hline
[131] & N + P & Encryption/Asymmetric using & & & & & +Group of end devices is authenticated at the same time & \\  & & ECC + Hashing & ✓(Identity) & 2 & C/F & I & –Location and Identity privacy are not analyzed and resistance to attacks are not studied & \\ \hline
[136] & N + P & N/A & ✓(audio samples as an identity) & 2 & D/H & I & +Low error rate and resistance to audio replay, changing distance, and same type device attacks. & –Location privacy is not analyzed \\ \hline
[115] & N + P & Encryption/Symmetric + & & ✓(Elliptic curve & 2 & C/F & I & +Privacy preservation is considered \\  & & ECC & & function) & & & -Threat and attacks are not considered \\ \hline
[104] & A + N + P & Encryption/Symmetric(AES) + & ✓(user Identity) & 2 & C/F & I & +Resistance to guessing, impersonation, and replay attacks & \\  & & Hashing & & & & & -Privacy preservation is not considered \\ \hline
[128] & N + P & Encryption/Symmetric + & & & & & +Resistance to DoS and impersonation, \\  & & Asymmetric using Hybrid & & ✓(user Identity) & 2 & C/F & I & considers data integrity and ensures user privacy \\  & & & (HLCE) & & & & -Location privacy is not analyzed. \\ \hline
[132] & P & N/A & ✓(writing process) & 2 & C/H & I & +Improve security without adding any extra hardware & \\  & & & & & & -No analysis for threats and attacks is done. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Ref\#** & **IoT Layer** & **Identity Context Credentials** & **Token Based? ** & **Proc. ** & **Arch. ** & **HW. ** & **Strength(+)/Weakness(–)** \\ \hline \multirow{4}{*}{[102]} & \multirow{4}{*}{A + N + P} & \multirow{4}{*}{Encryption/Symmetric} & \multirow{4}{*}{✓ (user Identity)} & \multirow{4}{*}{2} & \multirow{4}{*}{\(\mathrm{D}\,/\mathrm{H}\)} & \multirow{4}{*}{I} & +Less location update. \\  & & & & & & +Uses asymmetric links in VANET. \\  & & & & & & +Resistance to MITM, replay, and DoS attacks \\  & & & & & & -Privacy is not analyzed \\ \hline \multirow{4}{*}{[98, 99]} & \multirow{4}{*}{N + P} & \multirow{4}{*}{ \begin{tabular}{c} Encryption/Symmetric + \\ Asymmetric + Hashing \\ \end{tabular}  } & \multirow{4}{*}{x} & \multirow{4}{*}{3} & \multirow{4}{*}{D/H} & +Computation cost is efficient. \\  & & & & & +Resistance to the replay attack \\ \cline{1-1}  & & & & & -No analysis is done to the communication overhead \\ \hline \multirow{4}{*}{[92]} & \multirow{4}{*}{N + P} & \multirow{4}{*}{\ \begin{tabular}{c} Encryption/Symmetric+ \\ Hashing \\ \end{tabular}  } & \multirow{4}{*}{x} & \multirow{4}{*}{2} & \multirow{4}{*}{C/F} & +Resistance to DoS attacks and to packet loss \\  & & & & & +Computation and storage overhead \\  & & & & & +Low & +Low & +Low \\ \hline \multirow{4}{*}{[93]} & \multirow{4}{*}{N + P} & \multirow{4}{*}{ \begin{tabular}{c} Encryption/Symmetric+ \\ Hashing \\ \end{tabular}  } & \multirow{4}{*}{x} & \multirow{4}{*}{2} & \multirow{4}{*}{C/F} & +Resistance to DoS attacks and to packet loss \\  & & & & & +Computation and storage overhead \\  & & & & & +Low & +Low \\ \cline{1-1}  & & & & & +Low & +Low \\ \cline{1-1}  & & & & & +Low &