DOI: 10.5176/978-981-08-9266-1_BIDW2011_9

Authors: Albert .B. Jeng, Chien-Chen Tseng and Der-Feng Tseng

A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a scheme used to determine whether the user is a human or a malicious computer program. It has become the most widely used standard security technology to prevent automated computer program attacks from DoS attacks and Botnet. Actually, these attacks are more and more severe in cloud computing environment. Therefore, Google & Microsoft have used text-based CAPTCHA for account authentication in cloud computing for a long time. But almost all traditional text-based CAPTCHA on the market are breakable. In this paper, we first give an overview of CAPTCHA. Next, we discuss the security threats and attacks in CAPTCHA system.
Finally we propose a DWT-based image hashing algorithm to enhance performance of the Google CATPCHA system with rotated image and also give an analysis of its usability and security as well as its applicability to Cloud Computing authentication.

Keywords: Image Recognition CAPTCHA, DWT-Based, Image Hashing, Cloud Computing

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