Multiple SEIMCHA: Multiple semantic image CAPTCHA
Maryam Mehrnejad, Abbas Ghaemi Bafghi, Ahad Harati, Ehsan Toreini · 2011
Abstract — This paper presents a new semantic image CAPTCHA, called Multiple SEIMCHA. Multiple SEIMCHA system warps images by using geometric transformations and a 2d view of warped image is shown to user. Users should click on the upright orientation of warped image as a semantic. Multiple SEIMCHA evaluates user based on the idea of almost right response instead of completely right response. This idea uses hardness rate concept which is defined based on user response rate to images. The proposed system has a great response time and success rate as usability metrics and it is secure to bots.