## 2 Literature Review
Furthermore, the analysis of ESCI-AKA and other renowned security systems demonstrates that it has minimal computational and communication overhead, while offering strong security issues. As presented in Table 1, a variety of authentication techniques and factors that can be used to protect accounts and data are presented. Some of the most common techniques include multi-factor authentication (MFA), which requires users to provide two or more factors to authenticate, and encryption, which can protect data from unauthorized access. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** & \begin{tabular}{c} **Authentication** \\ **Technique** \\ \end{tabular} & \begin{tabular}{c} **Security Factors** \\ \end{tabular} & \
\begin{tabular}{c} **Factor Classification** \\ \end{tabular} &
\begin{tabular}{c} **Environment** \\ \end{tabular} \\ \hline
[38] & MFA + SHA 1 + AES- & \
\begin{tabular}{c} Encrypted Password, OTP based on OOB, \\ Email Account, Mobile Number, Count of \\ mouse clicks \\ \end{tabular} &
\begin{tabular}{c} SYK + SYH \\ \end{tabular} & Cloud Computing \\ \hline
[39] & MFA & PIN/Password, Biometrics, SMS OTP & SYH + SYA & Cloud Computing \\ \hline
[40] & MFA &
\begin{tabular}{c} Username-Password, Email Account, \\ Mobile Number, PIN, OTP \\ \end{tabular} & SYK + SYH & Cloud Computing \\ \hline
[41] & MFA & Secret-splitting key, OTP, IMEI number & SYH & Cloud Computing \\ \hline
[42] & MFA + CP-ABE &
\begin{tabular}{c} Username—Password, QR Code-based \\ OTP \\ \end{tabular} & SYK + SYH & Private Cloud Storage \\ \hline
[43] & MFA + CP-ABE &
\begin{tabular}{c} Username—Password, QR Code-based \\ OTP \\ \end{tabular} & SYK + SYH & Private Cloud Storage \\ \hline
[44] & MFA + VGG face &
\begin{tabular}{c} Username—Password, Security \\ Questions, Mobile OTP, Face image \\ \end{tabular} & SYK + SYH + SYA & Cloud Storage \\ \hline
[45] & MFA & Username—Password, OTP, Fingerprints & SYK + SYH + SYA &
\begin{tabular}{c} Cloud Storage in Smart \\ Banking \\ \end{tabular} \\ \hline
[46] & MFA + SSO & SMS OTP, Call on Phone, App approval & SYH & User’s Metadata in a Multi-Cloud \\ \hline
[47] & MFA &
\begin{tabular}{c} Face Verification, NFC Card \\ Authentication, Geofence Location, \\ Temporal Data Verification \\ \end{tabular} & SYH + SYA & Cloud-based Logistics \\ \hline
[48] & 2 FA + PSK & Username—Password, OTP & SYK + SYH &
\begin{tabular}{c} Cloud-based OTP \\ Services \\ \end{tabular} \\ \hline
[49] & MFA & \
\begin{tabular}{c} Username—Password, Secret key to AES \\ technique, Biometrics \\ \end{tabular} & SYK + SYH + SYA &
\begin{tabular}{c} Multiple Agents \\ Cloud-based Search \\ Engine \\ \end{tabular} \\ \hline
[50] & MFA + RSA + Hash & Contextual, Sign encryption, Iris \\ Func &
\begin{tabular}{c} Biometric \\ \end{tabular} & SYH + SYA & Cloud Health Care \\ \hline
[51] & MFA + Hash Func & \
\begin{tabular}{c} Username and Password, Biometrics, \\ Timestamp, Random number nonce \\ \end{tabular} & SYK + SYH + SYA &
\begin{tabular}{c} Cloud-based SDN \\ Health Care \\ \end{tabular} \\ \hline
[52] & MFA + ECC & \
\begin{tabular}{c} Username and Low Entropy, Password, \\ Fingerprints, Voice print, IMSI identity \\ \end{tabular} & SYK + SYH + SYA &
\begin{tabular}{c} Cloud-based Financial \\ Transactions \\ \end{tabular} \\ \hline
[53] & 2 FA & Username and Password, TOTP & SYK + SYH & Private Cloud \\ \hline
[54] & 2 FA & OTP, IoT Token & SYH &
\begin{tabular}{c} Cloud-based Web \\ Services \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: MFA different number of factors and techniques in cloud-based environments. The factors used for authentication can be divided into three classes: something you know, something you have, and something you are. Something you know (SYK) could be a password, PIN, or secret question. Something you have (SYH) could be a physical object, such as a security key or smartphone, or a digital object, such as a one-time password (OTP). Something you are (SYA) could be a biometric factor, such as a fingerprint or facial scan.