Abstract
Most websites use CAPTCHAs for privacy and security reasons. Most existing CAPTCHA methods require users to solve them by typing on a keyboard. With improved smartphones allowing users to browse the web using a smartphone, accessible CAPTCHA suited to smartphone features should be developed, keeping the abilities of visually impaired people in mind because typing text on soft keyboards is time-consuming, frustrating, and error-prone. A novel CAPTCHA has been proposed, TapCAPTCHA, which presents the CAPTCHA challenge using an audio clip and an image simultaneously. Instead of typing the text on a soft keyboard, the user responds by tapping on the phone screen. The user hears a CAPTCHA question regarding, for example, how many times the user will listen to a letter or a number in the ensuing clip, which is a distorted audio clip in which six digits are readout. After that, the user must tap the screen according to the number of times the user has heard the specified letter or number. For example, the user must tap on the screen two times after hearing the letter D twice. The novel method aims to remove the cognitive burden, eliminate access obstacles, and enable users to browse websites independently. The paper also discusses the initial study with 16 visually impaired users to examine the method's feasibility. The user study reveals that TapCAPTCHA is easy to learn, more accurate, and faster than traditional audio CAPTCHA. The success rate for TapCAPTCHA was 82.5%, while the audio CAPTCHA was 47.5%. The solving time for TapCAPTCHA was 11 and 119 s for the audio CAPTCHA. Ultimately, this research underscores the importance of designing a CAPTCHA method for visually impaired users that involves accessible gestures to reduce the error rate, effort, and cognitive load.