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...

approaches for designing image based CAPTCHAs are introduced. The first one-which is called Tagging image CAPTCHA-is based on pre-tagged images, using geometric transformations to increase security, and the second approach tries to enhance the first one...