A Gesture-based CAPTCHA Design Supporting Mobile Devices.

Abstract

In this paper we present the design and evaluation of a mobile user friendly CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) scheme based on our previous work. Unlike the commonly used character recognition based CAPTCHA schemes that require a user to type the distorted characters shown in an image to pass security checks, this scheme allows a user to use gestures to operate specific objects on the screen so as to complete a CAPTCHA quiz. Moreover, it uses partially processed or distorted textual instruction to prevent a bot from easily figuring out the objects to operate for retaining the security of the scheme as a bot cannot utilize context effects as easily as human users can. A comparative study is also conducted to understand the usability performance of this gestured based scheme against Google ReCAPTCHA, a popular character recognition scheme, where better usability has been reported with the former when both were used on smartphones.