Usability improvement in color constancy CAPTCHA

Abstract

CAPTCHAs have traditionally been used to deter bots, but ensuring protection against machine learning attacks has become difficult. To tackle this problem, we proposed a CAPTCHA based on color constancy, a human cognitive ability that is difficult for machines to reproduce. Although this method achieved high attack resistance while maintaining usability compared to existing CAPTCHAs, the response time increased due to the color selection operation. To address this, we changed the task to a click-type format while keeping the original concept. Our experimental results show that our method matches the response times of existing CAPTCHAs without compromising attack resistance.