## 4 Analysis and Discussion
### Analysis of PUF-Based Authentication and Its Applications
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Protocol** & **PUF** & \begin{tabular}{c} **Authentication** \\ **Schema** \\ \end{tabular} & \begin{tabular}{c} **Secure Storage** \\ **of Keys** \\ \end{tabular} & \begin{tabular}{c} **Storage of** \\ **CRPs** \\ \end{tabular} & \
\begin{tabular}{c} **Encryption** \\ **Methods** \\ \end{tabular} & **Platform Used** & **Major Issues** &
\begin{tabular}{c} **Major** \\ **Advantages** \\ \end{tabular} \\ \hline
[18] & SPUF & T2T & Yes & Yes & - & \begin{tabular}{c} Xilinx \\ XC/A35-T \\ FPGA \\ \end{tabular} & \
\begin{tabular}{c} Limited \\ multiple \\ cryptography \\ \end{tabular} &
\begin{tabular}{c} Does not \\ utilize \\ cryptography \\ \end{tabular} \\ \hline
[88] & Unspecified & T2T & No & Yes & \begin{tabular}{c} XOR, hash, \\ and ECC \\ \end{tabular} & \begin{tabular}{c} Xilinx FPGA \\ Zynq-7 \\ \end{tabular} & \
\begin{tabular}{c} Limited \\ encryption \\ \end{tabular} &
\begin{tabular}{c} Good \\ resistance \\ \end{tabular} \\ \hline
[89] & APUF & T2T & No & No & - & - & - &
\begin{tabular}{c} Very high \\ resilience \\ \end{tabular} \\ \hline
[90] & Unspecified & T2T & No & No & Hash & - & \
\begin{tabular}{c} Easy to attack \\ session key \\ \end{tabular} &
\begin{tabular}{c} Good communication \\ noerhead \\ \end{tabular} \\ \hline
[91] & Unspecified & T2T & Yes & Yes & Hash & - & \
\begin{tabular}{c} Does not \\ support PUF \\ attacker \\ caused by \\ noise \\ \end{tabular} &
\begin{tabular}{c} Covers various \\ types of \\ cryptographic \\ protocols \\ \end{tabular} \\ \hline
[92] & Unspecified & T2T & Yes & Yes & LBRAPS & - & - & - \\ \hline
[17] & Unspecified & T2T & Yes & Yes & - & \begin{tabular}{c} NodeMCU \\ v3 and \\ Raspberry Pi \\ 3B \\ \end{tabular} & \
\begin{tabular}{c} Too many \\ stages in \\ authentication \\ \end{tabular} &
\begin{tabular}{c} Good \\ resistance \\ \end{tabular} \\ \hline
[93] & XOR-PUF & T2T & Yes & Yes & XOR & \begin{tabular}{c} Xilinx \\ XC5 LVX110T \\ \end{tabular} & \
\begin{tabular}{c} Excessive \\ storage space \\ to store e-CRPs \\ \end{tabular} &
\begin{tabular}{c} Good \\ resistance \\ \end{tabular} \\ \hline
[94] & Unspecified & T2T & Yes & Yes & Hash, XOR & - &
\begin{tabular}{c} Excessive \\ storage space \\ \end{tabular} & Integrity \\ \hline
[95] & Unspecified & T2T & Yes & Yes & Hash, XOR & - & - &
\begin{tabular}{c} Evaluates PUF \\ attributes \\ \end{tabular} \\ \hline
[96] & Unspecified & T2T & Yes & Yes & EC, Hash & - &
\begin{tabular}{c} Many \\ parameters \\ \end{tabular} & - \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._agreement protocols are exposed to man-in-the-middle, impersonation, and replay attacks, as has been demonstrated [8]. Also, a proposed alternative scheme offers identity-based authentication and repudiation. Another challenge with PUFs is that they are prone to attacks if several PUFs' challenge-response pairs (CRPs) are subjected to an intrusion attack. A PUF-based, insubstantial, reliable authentication mechanism using binary string shuffling was proposed [85]. The key feature of this technique is that it is inexpensive yet secure. The server authentication is carried out before the underlying PUF becomes exposed, thus preventing it from being brute-forced. Finally, most researchers, such as [76; 77], when designing PUFs with IoT devices/servers use five methods of encryption that still suffer from cyberattacks, which are as follows:  
1: XOR gate encryption;  
2: Hash function methods;  
3: Block cipher methods;  
4: Elliptic-curve methods;  
5: AES methods. The significant vulnerability of these methods is a cloning cyberattack that puts the network/system under attack, so we must develop a smart framework with PUF technology that is able to keep IoT ecosystems safe. Any novel method must be strong and lightweight to face these challenges.