Embedded noninteractive continuous bot detection
Computers in Entertainment (CIE) - Theoretical and Practical Computer Applications in Entertainment
Balancing usability and security in a video CAPTCHA
Proceedings of the 5th Symposium on Usable Privacy and Security
SEMAGE: a new image-based two-factor CAPTCHA
Proceedings of the 27th Annual Computer Security Applications Conference
OTM'06 Proceedings of the 2006 international conference on On the Move to Meaningful Internet Systems: AWeSOMe, CAMS, COMINF, IS, KSinBIT, MIOS-CIAO, MONET - Volume Part I
A survey and analysis of current CAPTCHA approaches
Journal of Web Engineering
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Recognition of synthesized speech by a diphone synthesizer is thought to be easy for a machine due to the small variation of the synthesized speech. In this paper, we report the recognition rate of synthesized utterances in a noisy environment. Our experiments show that the performance of a HMM recognizer is not too bad even in the presence of background noise. These recognition results nearly approach the performance of a human. Thus, although there seems to be a gap in the ability of understanding synthesized speech with background noise between humans and computers, our results discourage using this gap to build an audio-based CAPTCHA (i.e., a reverse Turing test which can tell computers and humans apart). Moreover, we explored the possible use of a classification and regression tree to control the hardness of our CAPTCHA.