A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a challenge-response test used on the Internet to prevent bots from accessing web services that are designed for humans. In this paper, we propose Automatic Game-based CAPTCHA Generation (AGCG), in which an AI system generates games that, when played, distinguish between humans and bots. The gamebased CAPT...

Voice over IP (VoIP) introduces new ways of communication, while utilizing existing data networks to provide inexpensive voice communications worldwide as a promising alternative to the traditional PSTN telephony. SPam over Internet Telephony (SPIT) is one potential source of future annoyance in VoIP. A common way to launch a SPIT attack is the use of an automated procedure (bot), which generat...

A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is designed to distinguish humans from machines. Most of the existing tests require reading distorted text embedded in a background image. However, many existing CAPTCHAs are either too difficult for humans due to excessive distortions or are trivial for automated algorithms to solve. These CAPTCHAs also suff...

The increasing use of smart phones, tablets, and other mobile devices poses a significant challenge in providing effective online security. CAPTCHAs, tests for distinguishing human and computer users, have traditionally been popular; however, they face particular difficulties in a modern mobile environment because most of them rely on keyboard input and have language dependencies. This paper pr...

there has been an increasing concern about inactive drivers who would easily lead to road accidents and fatalities once return to driving. this study investigated the re-usability of traffic signs for inactive drivers with consideration of driver factors and cognitive sign features. fifty-seven hong kong chinese, who possessed a full driving license but had not driven for an extended period, co...