## 3 Overview of Physical Unclonable Functions
### PUF Types
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Study** & **Year** & **Type of PUF** & **Description** & **Limitations** \\ \hline
[50] & 2017 & Q-OPUF & A Q-OPUF uses nanometer-scale imperfections in pieces of 2D materials to achieve the functionality of a PUF. & Defect-free fabrication of monolayers is not possible, which results in bandgap alteration. \\ \hline
[51] & 2017 & Monolayer Deposition & The monolayer deposition PUF assesses the existence or deficiency of monolayer matter in different positions along with a growth substrate. & This technique examines only the variation in physical position on layers. \\ \hline
[52] & 2018 & Lanthanide PUF & The lanthanide PUF explores the locations of zeolites doped with lanthanide (III) ions through a substrate via a photoluminescence to replicate. \\ \hline
[53] & 1993 & Paper PUF & The paper PUF utilizes the distinctive marks of physical fibers such as currency to generate fingerprints. & Unique fingerprint can be established just by scanning the fiber/paper. \\ \hline
[54] & 2009 & CD PUF & The CD PUF utilizes the distinctive marks of the compact disk medium. It works by determining the length of the lands and pits of the CD. & A photodetector can be used for the determination of pits and lands. \\ \hline
[55] & 1994 & Magnetics PUF & The magnetic PUF uses randomness in ferromagnetic particle arrangement to generate unique magnetic swipe cards. & The inherit randomness in ferromagnetic particle arrangement is used to distinguish cards present in the database. \\ \hline
[56] & 2014 & Ring Oscillator PUF & A ring oscillator PUF works by analyzing the changes in the delay, which results in frequency of a signal propagating across an oscillator circuit formed of logic gates. & Simple circuitry. Can be implemented with the help of basic logic gates. \\ \hline
[57] & 2004 & Arbiter PUF & An arbiter PUF determines a system by analyzing the variations in the travel time of two electrical signals traveling through symmetrical paths. & Built from the on/off technique of the routing switches, giving a binary response depending on the faster path after this switching. \\ \hline
[58] & 2013 & Clock PUF & This type of PUF measures the changes in clock signal traveling velocity among signal lines, centered on the fabrication variation in these signal lines. & Now, due to the improvement in the design process, clock skew variations are almost negligible. \\ \hline
[59] & 2015 & VIA PUF & Such PUFs employ direct categorization of electronic modules. The VIA PUF uses the probability of physical connection between the electrical layers. & Approximately 50\% uniformity and uniqueness can be achieved. \\ \hline
[60] & 2000 & TV-PUF & The main idea of the threshold voltage (TV)-PUF is to quantify the discrepancy in threshold voltage of ICs at the point of production. & Number of transistors required. \\ \hline
[61] & 2009 & Power Distribution & The power distribution PUF works by defining the disparity in resistance of the power distribution system during the process of manufacturing an IC. & Additional components are added to each branch. \\ \hline
[62] & 2007 & SRAM-PUF & The static random-access memory (SRAM) PUF operates by finding the differences of transistor branches within SRAM. & Complexity of implementation as a fuzzy extractor on an FPGA is not known. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._