2019 Volume 8 Issue 3 Pages 55-60
We propose a new CAPTCHA scheme that uses random dot patterns (RDPs) to prevent highly-developed bots attacks. Human beings can recognize a moving figure filled by a RDP from a background that is filled by another RDP; however, it is impossible to find such figures when they are stationary. Since image recognition by bots is usually carried out frame by frame, it is hard for bots to recognize such moving figures. The proposed CAPTCHA scheme exploits this characteristic. Several experiments were carried out to confirm that the proposed CAPTCHA scheme is usable enough and has enough resistance against bot attacks.