We systematically study the design of image recognition CAPTCHAs (IRCs) in this paper. We first review and examine all IRCs schemes known to us and evaluate each scheme against th...
Bin B. Zhu, Jeff Yan, Qiujie Li, Chao Yang, Jia Li...
CAPTCHAs are automated Turing tests used to determine if the end-user is human and not an automated program. Users are asked to read and answer Visual CAPTCHAs, which often appear...
A CAPTCHA is a program that generates challenges that are easy to solve for humans but difficult to solve for computers. The most common CAPTCHAs today are text-based ones where a ...
Paul Baecher, Marc Fischlin, Lior Gordon, Robert L...
CAPTCHAs protect online resources and services from automated access. From an attacker’s point of view, they are typically perceived as an annoyance that prevents the mass creat...
Manuel Egele, Leyla Bilge, Engin Kirda, Christophe...
In this paper, we propose a new form of image-based CAPTCHA we term "scene tagging". It tests the ability to recognize a relationship between multiple objects in an imag...