# Biometrics for Internet-of-Things Security: A Review
## 3 Biometrics Overview
### Classification of Biometrics
#### 3.1.5 Others  
In addition to the common biometric traits introduced above, there are other traits, such as iris, palmprint, finger-vein, signature and keystroke. _Iris_: It is a thin, annular structure in the eye. The variabilities of iris patterns between different individuals are enormous. Iris has a great mathematical advantage compared with other biometric traits. Besides, the iris is an internal organ of the eye, making it less likely to be affected by the environment and thus staying stable over time [49]. _Palmprint_: It includes flexion creases and distinct ridges similar to a fingerprint. Minutiae and creases are common feature representations that are extracted for authentication purposes [50]. \begin{table}
\begin{tabular}{|c|c|c|c|c|c|} \hline
**Method for IoT Security** & \begin{tabular}{c} **Year of** \\ **Publication** \\ \end{tabular} & \begin{tabular}{c} **Type of** \\ **Biometric Traits** \\ \end{tabular} & **Databases** & **Performance** & **Hardware/Platform** \\ \hline \multicolumn{5}{|c|}{**Single-Modi Biometrics**} \\ \hline [PERSON] et al. [25] & 2016 & Fingerprint & - & - & ESP8266 NodeMCU \\ \hline [PERSON] and [PERSON] [26] & 2016 & Fingerprint & - & - & Raspberry Pi \\ \hline [PERSON] and [PERSON] [27] & 2016 & Fingerprint & - & - & Raspberry Pi 2 \\ \hline [PERSON] and [PERSON] [28] & 2018 & Fingerprint & - & - & Simulator on PC \\ \hline [PERSON] et al. [29] & 2019 & Fingerprint & - & - & Arduino board \\ \hline [PERSON] et al. [30] & 2019 & Fingerprint & FVC2002 DB3 & EER = 3\% & Simulator \\ \hline [PERSON] et al. [31] & 2020 & Fingerprint & Private & EER = 30\% & Raspberry Pi \\ \hline [PERSON] et al. [32] & 2016 & Face & FERET & RA = 99.5\% & Simulator \\ \hline [PERSON] and [PERSON] [33] & 2018 & Face & - & - & Simulator on Web Server (Apache) \\ \hline [PERSON] et al. [34] & 2020 & Face & - & - & Simulator on PC \\ \hline [PERSON] et al. [35] & 2020 & Face & WIDER FACE & RA = 60.7\% & Raspberry Pi 3 \\ \hline [PERSON] et al. [36] & 2016 & ECG & - & - & - \\ \hline [PERSON] et al. [37] & 2017 & ECG & MIT-BIH & RA = 97.78\% & Raspberry Pi 3 \\ \hline [PERSON] et al. [38] & 2019 & ECG & NIH PhysiBank & RA = 98.2\% & Simulator on PC \\ \hline [PERSON] et al. [59] & 2019 & ECG & PTB & RA = 98.76\% & Simulator \\ \hline [PERSON] and jun [40] & 2015 & Voice & - & - & - \\ \hline [PERSON] et al. [41] & 2020 & Voice & - & - & - \\ \hline [PERSON] et al. [24] & 2017 & Finger-vein & MMCBNU\_6000 & EER = 0.36\% & Simulator \\ \hline [PERSON] et al. [4] & 2019 & Iris & CASIA-Iris v3 & EER = 0.22\% & Simulator \\ \hline [PERSON] et al. [43] & 2019 & Iris & CASIA-Iris v4 & EER = 0.20\% & Simulator \\ \hline \multicolumn{5}{|c|}{**Multi-Modi Biometrics**} \\ \hline [PERSON] et al. [44] & 2016 & Face \& Iris & CASIA-Face v5 & RA = 99.1\% & Simulator \\ \hline [PERSON] et al. [45] & 2016 & Hand \& Gesture & - & - & - \\ \hline [PERSON] et al. [46] & 2019 & Face \& Voice & CSUF-S5 & \begin{tabular}{c} Fused: EER = 8.04\% \\ Face: EER = 14.05\% \\ Voice: EER = 43.76\% \\ \end{tabular} & Raspberry Pi 3 Model B \\ \hline [PERSON] et al. [47] & 2020 & \begin{tabular}{c} Fingerprint \& \\ Finger-vein \\ \end{tabular} & - & & Simulator on PC \\ \hline [PERSON] et al. [48] & 2021 & Ear \& Arm Gestures & \
\begin{tabular}{c} AWE \\ HMOG \\ \end{tabular} &
\begin{tabular}{c} Fused: EER = 5.15\% \\ Ear: EER = 20.80\% \\ Arm: EER = 10.60\% \\ \end{tabular} & Simulator \\ \hline \end{tabular}
\end{table} 
Table 2: The biometric methods for IoT security and corresponding information. _Finger-vein_: It is the pattern of blood vessels concealed under the finger skin and is distinct among individuals, including among identical twins [51]. _Signature_: This is a behavioral biometric trait often used in our daily business transactions. In signature recognition, the pressure, acceleration, speed and other attributes can be captured as features used in the matching process [52]. _Keystroke_: It is the typing pattern of an individual.