Protection through Intelligent and Multimedia Captchas

Protection through Intelligent and Multimedia Captchas

Wesam Al-Sudani (La Trobe University, Australia), Amit Gill (La Trobe University, Australia), Chen Li (La Trobe University, Australia), Jidong Wang (RMIT University, Australia) and Fei Liu (La Trobe University, Australia)
DOI: 10.4018/jaras.2012040103


The Complete Automatic Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a modern implementation of the Turing test. A CAPTCHA asks a series of questions which are supposed to be relatively easy for mature human beings but hard for machines to answer. A CAPTCHA, as its name suggests, is generally used as a tool to distinguish human beings from machines when the corresponding party is invisible in a remote site. There are many CAPTCHAs proposed and widely used in many Internet applications, with varied strength and performance. In this article, a review of current CAPTCHAs is presented. Analysis and comparisons are provided for various CAPTCHAs. Two types of new CAPTCHAs, intelligent and multimedia CAPTCHAs, are proposed. Our experiments have shown that the newly proposed CAPTCHAs have stronger protection than most existing CAPTCHAs and they can be applied to various web applications, such as e-commerce.
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2. Current Research On Captchas

CAPTCHAs can be classified into two main categories. The first operates on visual information, i.e., using images and the second one is audio-information based. Visual-based CAPTCHAs are the most widely applied and they counter attack three machine intelligences i.e., Optical Character Recognition (OCR), visual pattern recognition and a combination of both (Pope & Kaur, 2005; Szeliski, Avidan, & Anandan, 2000). The list below summarizes the most popular CAPTCHAs. A brief introduction on each of the CAPCHAs is presented.

  • Text based

    • Gimpy

    • EZ-Gimpy

    • PessimalPrint

    • Baffle Text

    • Scatter Type

  • Graphic based

    • Bongo

    • Pix

  • Audio based

  • Mouse intervention CAPTCHA

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