Two-Way Image Based CAPTCHA

CAPTCHA is a technology used to protect web applications from one of the malicious threats called BOT. CAPTCHA’s primary goal is to avail web services only to legitimate users and thereby foreseeing effective usage of web services. In this paper, a variant of image-based CAPTCHA is designed for visually challenged people. The main challenge is to identify human users from software robots. A novel two-way approach for image selection is designed to enhance the existing image-based CAPTCHAs. Randomly generated homography transformation function is used to find a match between the two images. Image-based CAPTCHAs have overwhelmed the text-based CAPTCHAs, and the proposed approach promises a better test for legitimate users to accomplish higher web security while retaining ease of use.