Annual Computer Security Applications Conference 2011 Technical Track Papers

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SEMAGE: A New Image-based Two-Factor CAPTCHA

We present SEMAGE (SEmanticallyMAtching imaGEs), a new image-based CAPTCHA that capitalizes
on the human ability to define and comprehend image content and to establish semantic relationships between
them. A SEMAGE challenge asks a user to select semantically related images from a given image set.
SEMAGE has a two-factor design where in order to pass a challenge the user is required to figure out the
content of each image and then understand and identify semantic relationship between a subset of them.
Most of the current state-of-the-art image-based systems like Assira [19] only require the user to solve the
first level, i.e., image recognition. Utilizing the semantic correlation between images to create more secure
and user-friendly challenges makes SEMAGE novel. SEMAGE does not suffer from limitations of traditional
image-based approaches such as lacking customization and adaptability. SEMAGE unlike the current Text
based systems is also very user friendly with a high fun factor. These features make it very attractive to
web service providers. In addition, SEMAGE is language independent and highly flexible for customizations
(both in terms of security and usability levels). SEMAGE is also mobile devices friendly as it does not
require the user to type anything. We conduct a first of its kind large-scale user study involving 174 users
to gauge and compare accuracy and usability of SEMAGE with existing state-of-the-art CAPTCHA systems
like reCAPTCHA (text-based) [6] and Asirra (image-based) [19]. The user study further reinstates our points
and shows that users achieve high accuracy using our system and consider our system to be fun and easy.


Shardul Vikram    
Texas A & M University
United States

Yinan Fan    
Texas A & M University
United States

Guofei Gu    
Texas A & M University
United States


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