Image Recognition CAPTCHAs

  • Monica Chew
  • J. D. Tygar
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3225)


CAPTCHAs are tests that distinguish humans from software robots in an online environment [3,14,7]. We propose and implement three CAPTCHAs based on naming images, distinguishing images, and identifying an anomalous image out of a set. Novel contributions include proposals for two new CAPTCHAs, the first user study on image recognition CAPTCHAs, and a new metric for evaluating CAPTCHAs.


Similarity Score User Study Anomaly Detection Pass Rate Human User 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Monica Chew
    • 1
  • J. D. Tygar
    • 1
  1. 1.UC Berkeley 

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