Making CAPTCHAs clickable

ABSTRACT

We show how to convert regular keyboard-entry CAPTCHAs into clickable CAPTCHAs. The goal of this conversion is to simplify and speed-up the entry of the CAPTCHA solution, to minimize user frustration and permit the use of CAPTCHAs on devices where they would otherwise be unsuitable. We propose a technique for producing secure clickable CAPTCHAs that are well suited for use on cell phones and other mobile devices. We support the practical viability of our approach by results from a user study, and an analysis of its security guarantees.

REFERENCES

• 1: BotBarrier.com. http://www.botbarrier.com/
• 2: K. Chellapilla, P. Simard. Using Machine Learning to Break Visual Human Interaction Proofs (HIPs). In Proc. of NIPS 2004.
• 3: Kumar Chellapilla , Kevin Larson , Patrice Simard , Mary Czerwinski, Designing human friendly human interaction proofs (HIPs), Proceedings of the SIGCHI conference on Human factors in computing systems, April 02-07, 2005, Portland, Oregon, USA [doi>10.1145/1054972.1055070]
• 4: Click Fraud, the dark side of online advertising. BusinessWeek, October 2006. http://www.businessweek.com/magazine/content/06_40/b4003001.htm
• 5: M. Davis. "Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy". http://www.mrc-cbu.cam.ac.uk/~mattd/Cmabrigde/
• 6: Asirra: a CAPTCHA that exploits interest-aligned manual image categorization, Proceedings of the 14th ACM conference on Computer and communications security, October 28-31, 2007, Alexandria, Virginia, USA [doi>10.1145/1315245.1315291]
• 7: P. Golle. Machine Learning Attacks Against the ASIRRA CAPTCHA. IACR Cryptology ePrint Archive, report 2008/126.
• 8: Google CAPTCHA. https://www.google.com/accounts/DisplayUnlockCaptcha
• 9: Ipsos Research. Face of the Web 2006. http://www.ipsos-na.com/news/pressrelease.cfm?id=3049
• 10: D. Lopresti. Leveraging the CAPTCHA problem. In Proc. of the Second International Workshop on Human Interactive Proofs, pp. 97--110. Springer Verlag, 2005.
• 11: G. Mori. Personal communication.
• 12: The Official CAPTCHA Site. http://www.captcha.net.
• 13: G. E. Rawlinson, "The significance of letter position in word recognition," PhD Thesis, Psychology Department, University of Nottingham, Nottingham UK, 1976.
• 14: L. von Ahn, M. Blum, N. J. Hopper and J. Langford. CAPTCHA: Using hard AI problems for security. In Proc. of Eurocrypt '03, pp. 294--311.
• 15: O. Warner. Kittenauth. http://www.thepcspy.com/kittenauth

INDEX TERMS

Primary Classification:
  K. Computing Milieux
  K.6 MANAGEMENT OF COMPUTING AND INFORMATION SYSTEMS
      K.6.5 Security and Protection (D.4.6, K.4.2)

General Terms:
Human Factors, Security

Keywords:
CAPTCHA, mobile devices, reverse Turing test, usability