The Evaluations of Deletion-Based Method and Mixing-Based Method for Audio CAPTCHAs
Audio CAPTCHA systems, which distinguish between software agents and human beings, are especially important for persons with visual disability. The popular approach is based on mixing-based methods (MBM), which use the mixed sounds of target speech and noises. We have proposed a deletion-based method (DBM) which uses the phonemic restoration effects. Our approach can control the difficulty of tasks simply by the masking ratio.
According to our design principle of CAPTCHA, the tasks should be designed so that the large difference of performance between the machines and human beings can be provided. In this paper, we show the experimental results that support the hypotheses as follows: (1) only using MBM, the degree of task difficulty can not be controlled easily, (2) using DBM, the degree of task difficulty and safeness of CAPTCHA system can be controlled easily.
KeywordsSecurity Visual Impalement Speech Recognition CAPTCHA Mixing-based Method Deletion-based Method
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- 2.Inaccessibility of CAPTCHA, Alternatives to Visual Turing Tests on the Web, W3C Working Group Note (November 23, 2005), http://www.w3.org/TR/turingtest/
- 3.Tam, J., Simsa, J., Hyde, S., Von Ahn, L.: Breaking Audio CAPTCHAs. In: Proceedings of NIPS (2008)Google Scholar
- 5.Warren, R.M.: Auditory Perception: A New Analysis and Synthesis. Cambridge University Press, Cambridge (1999)Google Scholar
- 6.Nakayama, M., et al.: CENSREC-4: Development of Evaluation Framework for Distant-talking Speech Recognition under Reverberant Environments. In: Proc. Interspeech (September 2008)Google Scholar
- 7.Hart, S.G., Staveland, L.E.: Development of NASA-TLX (Task Load Index): Results of empirical and theoretical research. In: Hancock, P.A., Meshkati, N. (eds.) Human Mental Workload. North Holland Press, Amsterdam (1998)Google Scholar