## 2 Comparison with Existing Surveys  
Much work in the area of passkeys focuses solely on specific technical challenges or potential solutions. While these provide great specific solutions, they do not address the larger picture or give an overview of the current challenges and potential improvements for passkey adoption.  
Table 1 shows the related work closest to ours. We compare the related work to our contribution by focusing on the following five properties:  
* Literature survey: Is the respective work performing a literature survey?
* Passkey focus: Is the respective work focusing specifically on passkeys? Not covering this aspect means that it covers passkeys but not as the primary content.
* Technical focus: Does it have a focus on the technical aspects of passkeys?
* Protocol focus: Does it have a focus on the protocol aspects of passkeys?
* Usability focus: Does it have a focus on usability aspects of passkeys?  
Table 1 clearly highlights the gap in our literature survey that covers challenges and potential improvements of passkeys from multiple angles, including a user-centric perspective alongside the technical and protocol focus.  
The existing literature that comes closest to our work are Refs. [8; 13; 14]. We, however, note that they do not focus on the usability aspects of passkeys. Ref. [13] conducts a literature review regarding the present authentication systems, with one part specifically focusing on passkeys from a technical perspective. They conclude their literature review with suggestions for an optimal authentication system. They do, however, not go into detail regarding the protocol and usability aspects of passkeys. Ref. [14] focuses solely on a review of passwordless authentication schemes, outlining a review of the recent literature regarding this topic, including protocol aspects and the history of passkeys. They do conclude that there is a conflict for passwordless authentication schemes between security and usability but do not go into detail regarding this. Further, due to their focus on historical development, they also do not cover the technical aspects of passkeys. Ref. [8] conducts a literature review regarding FIDO protocols alone, and therefore, it focuses  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Literature** & \begin{tabular}{c} **Literature** \\ **Survey** \\ \end{tabular} & \begin{tabular}{c} **Passkey** \\ **Focus** \\ \end{tabular} & \begin{tabular}{c} **Technical** \\ **Focus** \\ \end{tabular} & \
\begin{tabular}{c} **Protocol** \\ **Focus** \\ \end{tabular} &
\begin{tabular}{c} **Usability** \\ **Focus** \\ \end{tabular} \\ \hline
[1] & & & & x & & \\
[9] & & & x & & \\
[12] & & & x & & \\
[13] & x & x & x & & \\
[14] & x & x & & x & \\
[15] & & x & x & & \\
[8] & x & x & x & x & \\
[16] & & & x & & \\
[7] & & & x & & x \\
[17] & & & & & x \\
[18] & & & x & & \\ Our work & x & x & x & x & x \\ \hline \hline \end{tabular}
\end{table}
Table 1: Overview of related work and this work and the aspects it covers, ‘x’ indicates the respective property is covered in the listed related work.  
on passkeys from a technical and protocol perspective, highlighting that out of all FIDO protocols, FIDO2 is the most widely adopted protocol. It does, however, also fail to cover any of the usability aspects of passkeys in detail. The other related work focuses solely on the technical aspects of passkeys, analyzing or proposing passwordless-authentication protocols, without conducting a detailed literature review or focusing specifically on passkeys, etc.