Abstract
CAPTCHA, a short form of “Completely Automated Public Turing test to Tell Computers and Humans Apart”, is a computer program that can generate and grade tests that most humans can pass, but current computer programs cannot. This paper advances research on image-based CAPTCHA by incorporating the object segment collages. We first collect object segments from thousands of images by using our self-developed collection tool. Then, we create an image collage that compiles randomly selected object segments. To increase the difficulty for computer detection algorithms, we embed some features such as noisy background, object segment occlusion and object segment orientation update. We also develop a practical application using the newly proposed Object Segment Collage CAPTCHA. For the evaluation, we measure the accuracy performance of computer vs. human in solving CAPTCHA questions. In addition, we also conduct a user study over different CAPTCHA methods.
Highlights
When a computer program is able to generate a test to tell apart a human from a computer, it is known as a CAPTCHA (Completely Automated Public test to Tell Computers and Humans Apart) [1]
The server applications connect to the following two internal modules: a: CAPTCHA GENERATION Based on the SCAPTCHA Synthesis proposed in the previous subsection, we develop a module to generate CAPTCHA
We first run a user study by allowing users to try with different CAPTCHA methods and rank the methods based on their preference
Summary
When a computer program is able to generate a test to tell apart a human from a computer, it is known as a CAPTCHA (Completely Automated Public test to Tell Computers and Humans Apart) [1]. Websites have often been attacked by malicious programs that register for service on a massive scale. Those malicious programs are written to automatically consume a large amount of Web resources or bias results in online votes. This issue has driven researchers to the idea of CAPTCHA-based security to ensure that such attacks are not possible without human intervention, making them ineffective. CAPTCHA-based security methods have been proposed for related issues, e.g., countering Distributed Denial-of-Service (DDoS) attacks on Web servers [2]. A CAPTCHA acts as a security mechanism by requiring a correct answer to a question that only a human can reliably answer
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