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The Robustness of Google CAPTCHAs

Lookup NU author(s): Ahmad El Ahmad, Dr Jeff Yan, Mohamad Tayara

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This is the final published version of a report that has been published in its final definitive form by School of Computing Science, University of Newcastle upon Tyne, 2011.

For re-use rights please refer to the publisher's terms and conditions.

Abstract

We report a novel attack on two CAPTCHAs that have been widely deployed on the Internet, one being Google's home design and the other acquired by Google (i.e. reCAPTCHA). With a minor change, our attack program also works well on the latest ReCAPTCHA version, which uses a new defence mechanism that was unknown to us when we designed our attack. This suggests that our attack works in a fundamental level. Our attack appears to be applicable to a whole family of text CAPTCHAs that build on top of the popular segmentation-resistant mechanism of "crowding character together" for security. Next, we propose a novel framework that guides the application of our well-tested security engineering methodology for evaluating CAPTCHA robustness, and we propose a new general principle for CAPTCHA design

Publication metadata

Author(s): El Ahmad AS, Yan J, Tayara M

Publication type: Report

Publication status: Published

Series Title: School of Computing Science Technical Report Series

Year: 2011

Pages: 15

Print publication date: 01/09/2011

Source Publication Date: September 2011

Report Number: 1278

Institution: School of Computing Science, University of Newcastle upon Tyne

Place Published: Newcastle upon Tyne

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