The Effect of Applying Gaussian Blur Filter on Captcha's Security

Ariyan Zarei
2014 Computer Science & Information Technology ( CS & IT )   unpublished
Providing security for webservers against unwanted and automated registrations has become a big concern. To prevent these kinds of false registrations many websites use CAPTCHAs. Among all kinds of CAPTCHAs OCR-Based or visual CAPTCHAs are very common. Actually visual CAPTCHA is an image containing a sequence of characters. So far most of visual CAPTCHAs, in order to resist against OCR programs, use some common implementations such as wrapping the characters, random placement and rotations of
more » ... aracters, etc. In this paper we applied Gaussian Blur filter, which is an image transformation, to visual CAPTCHAs to reduce their readability by OCR programs. We concluded that this technique made CAPTCHAs almost unreadable for OCR programs but, their readability by human users still remained high.
doi:10.5121/csit.2014.4915 fatcat:e5d3bui5gre2xmp5wgu6tqjkvi