## 3 Overview of Physical Unclonable Functions
### PUF Attack  
PUF attacks aim to compromise the integrity and security of systems relying on PUF, thereby diminishing their effectiveness. Referred to as \"PUF attacks\" by researchers and academics, these incursions strategically exploit weaknesses in the implementation or design of security measures based on PUFs. PUFs capitalize on the inherent uniqueness and unpredictability arising from variations in device production, making them resistant to traditional cloning methods. As these attacks pose a potential threat to the integrity of PUFs, it is crucial to understand the diverse tactics employed. PUF attacks manifest in various forms, each targeting specific elements of the PUF architecture. Examples of these attacks include:  
Cloning Attacks: In a modeling attack, an adversary tries to create a mathematical model or replica of the PUF. This model could be based on measurements or observations of the PUF's responses to various challenges. If the attacker successfully models the PUF, they may be able to simulate its behavior and bypass security measures [71].  
Side-Channel Attacks: Side-channel attacks involve analyzing unintended information leakage from the PUF, such as power consumption or electromagnetic radiation. By monitoring these side channels, attackers may gain insights into the PUF's behavior and potentially extract sensitive information [72].  
Fault Injection Attacks: Attackers intentionally inject faults into the PUF or surrounding circuitry to disrupt normal operation. Techniques like voltage glitching or laser attacks may be employed to manipulate PUF responses and compromise their security [73].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Study** & **Year** & **Type of PUF** & **Description** & **Limitations** \\ \hline [63] & 2011 & Bistable Ring PUF & Based on the variation in a series of logic gates. & The BR-PUF oscillates for a relatively significant period before it stabilizes. \\ \hline \multirow{3}{*}{[64]} & \multirow{3}{*}{2011} & \multirow{3}{*}{MECCA PUF} & A memory cell-based chip authentication (MECCA) PUF comprises an arrangement of SRAM elements just like the SRAM-PUF and is based on the essential transistor deviation. \\ \cline{3-5}  & & & Analyzing difference in the elements’ dynamic random-access memory (DRAM) cells. & Performance is temperature-dependent. \\ \hline \multirow{3}{*}{[66]} & \multirow{3}{*}{2010} & \multirow{3}{*}{Glitch PUF} & The glitch PUF works by analyzing the complicated variation in glitches that are created because of the delay-based circuits. \\ \cline{3-5}  & & & & \\ \hline \multirow{3}{*}{[56]} & \multirow{3}{*}{2014} & \multirow{3}{*}{TERO-PUF} & A new silicon PUF based on a transient effect ring oscillator. & N/A \\ \hline \multirow{3}{*}{[67]} & \multirow{3}{*}{2006} & \multirow{3}{*}{Coating PUF} & Such PUFs work by measuring the capacitance across a pair of comb-shaped sensors in the top layer of an integrated circuit. & Eliminating/reducing the resistance in this type of construction against side-channel attacks is challenging. \\ \hline \multirow{3}{*}{[68]} & \multirow{3}{*}{2014} & \multirow{3}{*}{CNPUF} & Carbon nanotube field-effect transistors (CNFETs) have excellent electrical properties. These distinguished physical features that can be used to create a CNPUF. & There is a trade-off between power consumed and security. \\ \cline{3-5}  & & & The Q-EPUF PUF uses fluctuations in tunneling widths through quantum wells in resonant tunneling diodes. & N/A \\ \hline \multirow{3}{*}{[70]} & \multirow{3}{*}{2016} & \multirow{3}{*}{Self-Assembly PUF} & These PUFs use the physical phenomenon of molecular self-assembly. & Limited semiconducting purity and non-ideal assembly. \\ \cline{3-5}  & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: _Cont._