## 3 Results
### RQ2: What Pass-Objects Are Used for Authentication in These Methods?
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**ID** & **Method** & **Author** & **Strengths** & **Weaknesses** \\ \hline S1 & [PERSON] and Waghmare scheme & [PERSON] and Waghmare [26] & It is simple to implement and has the potential to defend against shoulder-surfing attacks. Capable of mitigating SSAs without weakening password strength. & Vulnerable to multiple observations of shoulder-surfing attacks (MOSSAs). \\ S2 & [PERSON] et al. scheme & [PERSON] et al. [27] & [PERSON] et al. [27] & Without weakening password strength. & Weak against observational attacks involving multiple sessions. \\ S3 & 3 DGUA & [PERSON] et al. [28] & Simple to operate. & Susceptible to direct observation attacks on account that the images that are registered. \\ S4 & PassMatrix & [PERSON] et al. [29] & Use the login indicator to mitigate the direct observation attack. & Open to potential compromises involving video recording and multiple observations. \\ S5 & [PERSON] et al. scheme & [PERSON] et al. [30] & [PERSON] et al. [30] & Opable of mitigating direct observation attacks using decoy images. & Vulnerable to MOSSAs and video-recorded shoulder-surfing attacks (VRSSAs). \\ S6 & PRGUARSS & [PERSON] et al. [31] & Opable of mitigating direct observation attacks. & VRSSAs because registered images are fixed and always connected with a line. \\ S7 & [PERSON] et al. scheme & [PERSON] et al. [32] & Potential to protect against direct observation attacks. & Vulnerable to MOSSAs and VRSSAs. \\ S8 & LocPass & [PERSON] et al. [33] & Potential to thwart SSAs. & The authentication time may be high due to the navigation involved. Susceptible to direct observation attacks on account that a user logs in with only the registered images. Vulnerable to MOSSAs and VRSSAs because the system always selects and displays registered images. \\ S9 & PassPage & [PERSON] et al. [34] & Easy and convenient to use. & Susceptibility to direct observation attacks on account that a user logs in with only the registered images. Vulnerable to MOSSAs and VRSSAs because the system always selects and displays registered images. \\ S10 & [PERSON] et al. scheme & [PERSON] et al. [35] & Use a pass-string to mitigate direct observation attacks. & VRSSAs because the system always selects and displays registered images. Susceptible to SSAs because an adversary can easily observe the code entered by the user and associate it with registered images. Susceptible to direct observation attacks on account that the images that a user clicks on the images that are registered. Susceptible to SSAs if multiple authentication sessions are video recorded. \\ S11 & MFAS & [PERSON] and [PERSON] [36] & Potential to protect against keyloggers. & Susceptibility to detect observation attacks on account that a user logs are registered images. Susceptible to direct observation attacks on account that the images that a user clicks on the images that are registered. Susceptible to SSAs because authentication sessions are video recorded. \\ S12 & [PERSON] & [PERSON] et al. [37] & Easy and convenient to use with an alphanumeric password. & Susceptible to direct observation attacks on account that the images that a user clicks on are the images that are registered. Susceptible to SSAs if multiple authentication sessions are video recorded. \\ S13 & [PERSON] & [PERSON] et al. [38] & Capable of mitigating direct observation attacks. & Susceptible to SSAs if multiple authentication sessions are video recorded. \\ S14 & [PERSON] & [PERSON] et al. [39] & Potential to prevent shoulder-surfing attacks using deformed images. & Vulnerable to SSAs because registered images would always appear in the same fixed locations. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Overview of the contributions and limitations of the selected recognition-based systems.