# Enhancing Security of Online Interfaces: Adversarial Handwritten Arabic CAPTCHAs Generation
## 2 Literature Review
### Latin Handwritten CAPTCHAs  
Latin handwritten CAPTCHAs have received a great deal of attention in recent times [19; 20]. That is, handwritten CAPTCHAs have emerged as an alternative to text-based versions, which are increasingly susceptible to automated attacks [21]. These systems leverage the human ability to recognize handwriting, a task that remains challenging for machines [22]. Previous research has integrated various language scripts into multilingual CAPTCHAs, including English, Arabic, Spanish, and French [6]. Additionally, a system was developed in [21] to synthesize English handwriting and assess its security against automated solvers, with subsequent studies, like [23], expanding this approach to include multiple languages.  
[PERSON] and [PERSON] [19] were the first to investigate the use of handwritten CAPTCHAs, highlighting the difference in abilities between humans and machines in reading handwritten words. They also examined the difficulties presented by handwritten text images for computers and their real-world users [24]. The researchers also suggested a visual CAPTCHA with handwritten image evaluation [25] and an interactive human proof system employing handwriting identification [26].  
Generating and evaluating handwritten CAPTCHAs incorporating Latin characters has seen limited exploration in previous research. [PERSON] et al. [22] investigated features of Latin script that could impact recognition. [PERSON] and [PERSON] [27] suggested a technique for creating synthetic handwritten CAPTCHAs and assessed their effectiveness.  
\begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Study** & **CAPTCHAs Type** & **Description** \\ \hline
[14; 15] & Interactive-based CAPTCHAs & Require users to perform interactive tasks like dragging and dropping shapes \\ \hline
[9; 18] & Text-based CAPTCHAs & Present distorted text that users must correctly decipher \\ \hline
[13] & Audio CAPTCHAs & Contain audio clips of words/numbers for users to identify \\ \hline
[17] & Interactive video-based CAPTCHA & Invole interaction with videos, such as pausing at an object \\ \hline
[10; 12] & Puzzle-Based CAPTCHAs & Comprise puzzles that must be solved correctly \\ \hline
[11] & Image-based CAPTCHAs & Feature images/objects for users to view and identify \\ \hline
[16] & Game-based CAPTCHAs & Implement games challenges \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of CAPTCHA types.  
[PERSON] and [PERSON] [28] developed a random handwritten CAPTCHA method for enhancing web security.  
In addition to their earlier research, [PERSON] and [PERSON] [20] studied the creation and application of handwritten CAPTCHAs, while [PERSON] et al. [29] examined the use of cognitive factors in enhancing web security with CAPTCHAs. [PERSON] and [PERSON] [30] explored leveraging human perception and visual object interpretation for the same purpose.  
[PERSON] [21] aimed to build upon past efforts by developing a novel Latin handwritten CAPTCHA system. Techniques included synthesizing representations of connected Latin script resembling natural handwriting variability. Both automated and human evaluations were employed to assess the security and usability.  
However, there has been limited research focused on generating and evaluating handwritten CAPTCHAs that incorporate Latin characters. For example, a study in [22] investigated characteristics of Latin script that could influence recognition.