Evaluating the accessibility and usability of a universal CAPTCHA based on gestures for smartphones
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Evaluating the accessibility and usability of a universal CAPTCHA based on gestures for smartphones Mrim Alnfiai1
© Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a test used on web sources to differentiate between humans and automated computer robots. CAPTCHA on smartphone platforms is fraught with difficulty for users with visual and hearing impairment. For deaf users, speech as a CAPTCHA input method is not useable in noisy environments. For blind users, typing a letter requires to search for its button on the virtual keyboard; thus, it is time-consuming. Gesture input is therefore a solution for smartphone applications, as neither vision nor hearing is required. This research developed new CAPTCHAs, HearAct and SeeAct, which are suitable for blind, deaf, and sighted users. These CAPTCHAs provide two ways of presenting universally accessible challenges: (1) Users see an image, identify an object in the image and then identify a word that corresponds with that object (SeeAct); (2) users listen to an object’s sound (the “sound-maker”, e.g., a dog) and identify the sound-maker (HearAct). HearAct and SeeAct CAPTCHAs provide both audio and an image of the sound maker, simultaneously. In both, users analyze a word to determine whether the word has a stated letter and then use gestures to answer. If the identified word has the letter, the user must tap; if not, they must swipe. Considering usability and accessibility, as compared to most common audio CAPTCHAs (used by blind users) and text CAPTCHAs (used by deaf and sighted users), results indicate significantly improved accessibility using both HearAct and SeeAct CAPTCHAs. Gesture-based HearAct and SeeAct CAPTCHA have a higher success rate, are more accessible, require less solving time, and are preferred by all users over the traditional CAPTCHA method.
1 Introduction The Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a test used to differentiate humans from automated bots when accessing online websites or creating online accounts or emails. CAPTCHA mechanisms protect websites from automated internet attacks and prevent software from accessing online resources by blocking bot execution procedures [34]. As a result, CAPTCHA mechanisms are used by numerous websites to minimize security risks and provide safe storage space for website administrators. Based on accessibility criteria, CAPTCHA challenges should be both simple for humans and complex for automated programs (bots) [4, 17].
* Mrim Alnfiai [email protected] 1
Department of IT, College of CIT, Taif University, Taif – Al‑Haweiah, P. O. Box 888, Taif ZIP code 21974, Kingdom of Saudi Arabia
Web services provide a wide range of social and financial activities and services. While most websites use CAPTCHA mechanisms to prevent unsecure access, unfortunately, most existing mechanisms are not suitable for smartphones and make accessing websites co
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