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CAPTCHA and Accessibility Is This the Best We Can Do?

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CAPTCHA and Accessibility Is This the Best We Can Do? CAPTCHA and Accessibility Is This the Best We Can Do? Lourdes Moreno, María González and Paloma Martínez Computer science department, Universidad Carlos III de Madrid, Av. Universidad, 30, Leganes, Spain Keywords: Web Accessibility, CAPTCHA. Abstract: Web access is affected by a great amount of accessibility issues that do not allow some users to access all information presented. Therefore, Web accessibility is an important issue because everybody should access Web content independently of their access features. Among these accessibility issues, a Web content element that interferes with Web accessibility is a CAPTCHA. A CAPTCHA is a challenge-response test used to determine whether or not the user is a human instead of a computer or a robot. This type of element causes accessibility barriers especially to users with disabilities. This paper presents an overview about Web accessibility and CAPTCHA. Besides, an analysis of the accessibility barriers and a solution proposal depending on the type of disability is provided. Moreover, a survey of CAPTCHA approaches is introduced and its results are shown. With the knowledge gathered, a data discussion is provided. The lesson learned is that the CAPTCHA objective must be that security checks should be responsibility of websites or servers, that is, they cannot be delegated to the user. 1 INTRODUCTION about it. The motivation of this paper is to carry out a The Web sites security directive uses Completely study concerning accessible CAPTCHA taking into Automated Public Turing test to tell Computers and account the access features of the users with Humans Apart (CAPTCHA) in order to avoid input disabilities. After analysing all this information, that has been generated by a computer or a bot, and accessibility barriers to perceive, to solve, to access authenticate that whoever is accessing is a human (answer -typing, to pointing, ..- and submit) of the user. There is a trend to use this content element on CAPCHA for several user profiles of people with many websites and sometimes it provokes disabilities have been distinguished and proposed accessibility barriers that avoid Web content access solutions are provide in each user profile. to people with disabilities. Besides, a lot of The remainder of the paper is organised as CAPTCHA techniques have emerged that cheat follows: Section 2 covers the background of through software allowing computers or robots to accessibility and some CAPTCHA issues. Section 4 access the content and that include more introducs an analysis of accessibility barriers and a accessibility barriers. Users with disabilities need solution proposal. In section 5, a survey of several assistive technology to access to the Web, and CAPTCHA approaches are shown. Finally, CAPTCHA techniques. CAPTCHA techniques must discussion of the data and lessons learned are take account it to provide a supported access to this presented in Section 7. technology. In order to deal with these accessibility barriers, most users have to be helped by other people. This fact has caused that some people protest 2 BACKGROUND against it as in the case of Australia (Hawkins, 2013) to ask for the elimination of Web CAPTCHA and A large increase of CAPTCHA on the Web is the use of other ways of security such as SMS or observed. The growth of CAPTCHA is due to it is a mails. On the other hand, it is also important to security mechanism which can be introduced easily.. highlight that security should be included by the But it has not been properly carried. The server avoiding that users have to be concerned accessibility has not been in mind when this element Moreno L., González M. and Martínez P.. 115 CAPTCHA and Accessibility - Is This the Best We Can Do?. DOI: 10.5220/0004858901150122 In Proceedings of the 10th International Conference on Web Information Systems and Technologies (WEBIST-2014), pages 115-122 ISBN: 978-989-758-024-6 Copyright c 2014 SCITEPRESS (Science and Technology Publications, Lda.) WEBIST2014-InternationalConferenceonWebInformationSystemsandTechnologies has been integrated on the Web. the bot. Besides, designers should take into account some techniques such as: 2.1 Web accessibility & CAPTCHA . Technique G143 (Providing a alternative text that describes the purpose of the CAPTCHA): It is essential to achieve an accessible Web in order the purpose of the technique is to provide to provide equal access and equal opportunity to information via the alternative text that people with diverse abilities. Therefore, an identifies the non-text content as a CAPTCHA. accessible CAPTCHA should be a mechanism that . Technique G144 (Ensuring that the Web Page avoids the access of robots but not the access of a contains another CAPTCHA serving the same human user independently of his language, purpose using a different modality): the knowledge or whether the user has any kind of purpose of the technique is to reduce occasions disability that hinders his interaction with Web in which a user with a disability cannot content. complete a CAPTCHA task. Currently, the use of CAPTCHA causes a great Others international standards found related to number of accessibility barriers. In order to avoid accessibility are: the ISO 9241-151, Ergonomics of these barriers, designers have to know what the main human-system interaction - Guidance on World standards and regulations have to follow in order to Wide Web user interface, the ISO 9241-171, design an accessible CAPTCHA. Every website has Ergonomics of human-system interaction - Guidance to be designed according to accessibility standards on software accessibility that provide guidance on that allow users to access Web content software accessibility and the ISO/IEC TR 29138-1, independently whether or not they have a disability. Information technology - Accessibility Regarding accessibility standards is important to considerations for people with disabilities - User highlight the World Wide Web Consortium (W3C) needs summary. with its Web Accessibility Initiative (WAI) (W3C, 2012). WAI includes various works such as User 2.2 Disabilities Agent Accessibility Guidelines (UAAG), Authoring Tool Accessibility Guidelines (ATAG) and the most A great amount of web applications and websites important standard, the Web Content Accessibility present accessibility problems and they are not Guidelines (WCAG) (W3C, 2008), adapted to people taking into account their type of WCAG 2.0 is the set of accessibility guidelines disability. The main types of disabilities are: Visual most referenced in the world and since 2012 is a disability (blindness, low vision and color- standard ISO/IEC 40500:2012, Information blindness), Auditory disability (deaf and hearing technology - W3C Web Content Accessibility loss), Motor disability (muscular dystrophy, multiple Guidelines (WCAG) 2.0). Following this standard, sclerosis, etc.) and Cognitive disability (WebAIM, there are several initiatives in different countries 1999). related to Web accessibility such as: Section 508, Besides this type of disability, it is important to BITV 2.0, RGAA, AODA among others. These take into consideration the degrees of a disability. initiatives are similar to WCAG 2.0, being in some For example, there are four degrees of hearing loss, case a copy of it. mild, moderate, severe and profound. Following the WCAG 2.0, the Success Criterion On the other hand, a user can have more than one 1.1.1 indicates that Non-text content explicitly disability or multiple disabilities. For example, many excludes the requirement to supply a text alternative people develop age-related impairments. These to a CAPTCHA image for this very reason. But that combinations of disabilities cause users have to face doesn't let the developer off the hook, because it more accessibility barriers. required that: …text alternatives that identify and People with disabilities sometimes use other describe the purpose of the non-text content are technology (software and hardware), called provided, and alternative forms of CAPTCHA using Assistive Technology (AT), to interact with the output modes for different types of sensory Web. There are types of AT that allow users to perception are provided to accommodate different access web content. For example, for visual disabilities (W3C, 2008). disability, screen readers, adapted keyboard, screen The difficulty in making a CAPTCHA image magnifiers and braille embossers can be highlighted. accessible is that providing a text alternative of the The review carried out in this paper may be image, as required for screen reader users to helpful to designers so that they can keep in mind understand the content, also supplies the answer to several aspects regarding type of disabilities that 116 CAPTCHAandAccessibility-IsThistheBestWeCanDo? have to be taken into account when they are . Limited-use accounts: creates limits for new accomplished the design, such as: the variety of users can mean of making sites unattractive types and degrees of disabilities and the technology targets to robots. Having to take a trial-and-error that can help them to allow users to access Web approach to determine a useful technique is a content. downside. Non-interactive checks: non-interactive 2.3 CAPTCHA mechanism can be used instead of CAPTCHA or interactive approaches. Spam filtering and The aim of CAPTCHA is to avoid robots and heuristic checks are two non-interactive computers can register in a forum, create an email approaches. account or access to a public service. This element is . Federate identity systems: tries to set an identity also used as security mechanism when a user of each client and maintain it across all sites that introduces three times a wrong password trying to use the same service. This solution presents three access a website. On the other hand, Google uses a approaches: single sign-on, public-key CAPTCHA called reCAPTCHA (Google, 2013) in infrastructure solutions and biometrics. order to improve book digitalization and stop spam . Other approaches: one approach is the use of at the same time. artefacts of identity such as credit cards or The most common form of CAPTCHA is national ID.
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