The Community for Technology Leaders
Computer and Information Technology, International Conference on (2010)
Bradford, West Yorkshire, UK
June 29, 2010 to July 1, 2010
ISBN: 978-0-7695-4108-2
pp: 552-559
An increasing number of public web services have attempted to prevent exploitation by bots and automated scripts, by requiring a user to solve a Turing-test problem, namely a ”Completely Automated Public Turing test to tell Cmputers and Humans Apart (CAPTCHA)”, before they are allowed to use web services. In this paper, we present an effective image-based CAPTCHA based on the orientation of N-gonal cropped sub-images as a solution of CAPTCHAs. Our CAPTCHA is based on the difficulty of detecting the orientation of N-gonal sub-images. In our CAPTCHA, the number of orientations and the crop size are important considerations, since our CAPTCHA requires users to find the orientation of sub-images cropped in the form of a regular polygon. So, we discuss usability of our CAPTCHA and the efficient values of the number of orientations and the crop size through user experiments and SVM-based machine learning tests in this paper.
Image-based CAPTCHA, Usability, Random attack, Machine learning, Perceptual recognition

W. Chung, H. Cho, J. Kim and S. Kim, "Detecting the Orientation of N-gonal Cropped Sub-images and Its Application," 2010 IEEE 10th International Conference on Computer and Information Technology (CIT), Bradford, 2010, pp. 552-559.
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