Effects of Text Rotation, String Length, and Letter Format on Text-based CAPTCHA Robustness
Chatpong Tangmanee · Journal of Applied Security Research · 2016
CAPTCHA, standing for Completely Automated Public Turing test to tell Computers and Humans Apart, has been adopted as a security check. One way to assess robustness of a text-based CAPTCHA test is to use optical letter reader (OCR) software to read it. If the reading fails, the design is robust. Though many design features have been examined, no research has investigated the effects of text rotation, string length, or letter format on CAPTCHA robustness. Fourteen hundred sixty four text-based CAPTCHA tests were created based on the three variables. The main effects of all three variables and few of the interaction effects on robustness were significant. The findings have both theoretical and practical contributions.