Authors: Lourdes Moreno, María González, Paloma Martínez WEBIST2014: 10th International Conference on Web Information Systems and Technologies (April 2014, Barcelona, Spain). Proceedings of the 10th International Conference on Web Information Systems and Technologies (WEBIST 2014) , SCITEPRESS, ISBN: 978-989-758-0, Volumen: 2, Páginas: 115-122 CAPTCHA and accessibility. Is this the best we can do?

1. CAPTCHA and accessibility. Is this the best we can do?
Lourdes Moreno, María González-García and Paloma Martínez
Computer Science Department, Universidad Carlos III de Madrid, Spain
{lmoreno, mgonza1, pmf}@inf.uc3m.es
10th International Conference on Web Information Systems and Technologies (WEBIST), 03-05 April 2014
MOTIVATION: There is a trend to use a CAPTCHA on many websites, but sometimes it
provokes accessibility barriers that avoid the Web content access.
1) Background and issues for CAPTCHA & Web Accessibility:
 W3C: WAI, WCAG 2.0 (SC 1.1.1 : Technique G143, G144)
 Designers have to know what the main standards and regulations have to follow in order to design an accessible
CAPTCHA.
 Solutions according to W3C document “Inaccessibility of CAPTCHA - Alternatives to Visual Turing Tests on the
Web”.
 Related Work
 Disability: Many accessibility barriers with CAPTCHAs!
 Assistive Technology (AT)
 Types of disability and different degrees
SOLUTION SPACE ANALYSIS
TYPE OF DISABILITY
ACC. BARRIERS
[PERCEIVE,
SOLVE, ACCESS ]
HOW TO ACCESS CAPTCHA PROPOSED SOLUTION
Visual X X (*) AT (magnifier or screen reader)
Perception: auditory modality
WCAG 2.0 must be achieved
Auditory Perception: no problem (visual modality)
WCAG 2.0 must be achieved
Motor X (*) Keyboard or AT WCAG 2.0 must be achieved
Cognitive X X (*) Difficulties to understand and solve
CAPTCHA
Limiting the degree of difficulty
WCAG 2.0 must be achieved
Visual and auditory X X (*) AT (Braille Displays) WCAG 2.0 must be achieved
Visual and motor X X (*) AT (screen reader, magnifier) only
keyboard
Perception: auditory modality
WCAG 2.0 must be achieved
Visual and cognitive X X X (*)
AT (screen reader, magnifier),
Difficulties to understand and solve
CAPTCHA
Perception: auditory modality
Limiting the degree of difficulty
WCAG 2.0 must be achieved
Auditory and motor X (*) Keyboard or AT
Perception: no problem (visual modality)
WCAG 2.0 must be achieved
Auditory and cognitive X X (*) Difficulties to understand and solve
CAPTCHA
Perception: no problem (visual modality)
Limiting the degree of difficulty
WCAG 2.0 must be achieved
Motor and cognitive X X (*)
Keyboard or AT
Difficulties to understand and solve
CAPTCHA
Limiting the degree of difficulty
WCAG 2.0 must be achieved
2) Scenarios defined according to types of disability:
(*) If web content does not fulfil the WCAG 2.0
CAPTCHA
APPROACHES
1: Form test
with simple
question
2: Form test
with simple
(2)
3: Empathy
to solve
4:
Advertisement
to solve
5: Recognising
to an animal
6: Access
to the
video
7: 3D object
recognition
8: Composing
a phrase
9: Solving
a Mini
game
10: Moving
the sliders
11:
HoneyPot
VISUAL
 (*)  (*) 
X X X X  X  (*) 
AUDITORY
  
X
  
 
 
MOTOR
      
X X  (*) 
COGNITIVE
X X X 
X  X  X  
3) CAPTCHA survey summary:
(*) High interdependence with the- WCAG 2.0 Compliance- and support with keyboard and AT (screen reader).
 Users with cognitive disabilities
have more difficulties followed by
blind users
 It is possible to design
proposals CAPTCHA that can
present a high level of
accessibility, but unfortunately
accessibility barriers continue
happening.
AND CONCLUSIONS:
 The security should be included
by the server avoiding that users
have to be concerned about it.
 It should continue working on
security solutions that prevent the
use of the CAPTCHA.
 Some solutions can be used:
system to control spam such as
Approach 11 (HoneyPot) or email
instead of using a CAPTCHA.
4) DISCUSSION:
This work includes:
1) Background and issues for CAPTCHA & accessibility.
2) Scenarios defined according to types of disability: analysis to distinguish accessibility barriers to
perceive, to solve, to access (answer and submit) the CAPTCHA for user profiles of people with
disabilities.
3) A survey of the CAPTCHA current solutions which include accessibility features.
4) To provide a final conclusions and solution proposal.
ACKNOWLEDGEMENTS: This research work is supported by the Research Network MAVIR (S2009/TIC-1542 (see www.mavir.net/)) and the MULTIMEDICA project (TIN2010-20644-C03-01).