Designing Human Friendly Human Interaction Proofs (HIPs) Kumar Chellapilla, Kevin Larson, Patrice Simard and Mary Czerwinski Microsoft Research Presented by Shaohua Xie March 22, 2005

OUTLINE  Introduction  Definitions  User Study I  User Study II  Conclusion  References

Introduction HIPs, or Human Interactive Proofs, are challenges meant to be easily solved by humans, while remaining too hard to be economically solved by computers. An example character based HIP

Introduction HIPs are increasingly used to protect services against automatic script attacks. Mailblocks HIP samples.

Introduction MSN HIP samples. Register.com HIP samples.

Introduction EZ-Gimpy HIP samples.

Introduction YAHOO! HIP samples. Ticketmaster HIP samples.

Introduction Google HIP samples.

OUTLINE  Introduction  Definitions  User Study I  User Study II  Conclusion  References

Definitions  Plain text => Global Warp  Plain text => Local Warp =>

Definitions  Translated Text Level 10  Rotated Text Level 25 Level 40 Level 15 Level 30 Level 45

Definitions  Scaled Text Level 20 Level 35 Level 50

OUTLINE  Introduction  Definitions  User Study I  User Study II  Conclusion  References

User Study I  HIPs that only varied on one parameter of distortion are presented to users.  Accuracy: the percentage of characters correctly recognized.  For the parameter levels tested on plain, translated, rotated or scaled text HIPs, users were at 99% correct or higher.

User Study I  Global Warp Text Level 180Level 270Level 360

User Study I  Local Warp Text Level 30Level 55Level 80

OUTLINE  Introduction  Definitions  User Study I  User Study II  Conclusion  References

User Study II  Unidimensional HIPs has been systematically broken, with a success rate of 5% or greater at a rate of 300 attempts per second [2,12].  Arcs and baselines are added to make HIPs very hard for computers to break.

User Study II  Thin Arcs that intersect plus baseline #Arcs: 0#Arcs: 18#Arcs: 36

User Study II  Thick Arcs that intersect plus baseline

User Study II  Thick Arcs that don’t intersect plus baseline #Arcs: 0#Arcs: 18#Arcs: 36

OUTLINE  Introduction  Definitions  User Study I  User Study II  Conclusion  References

Conclusion  Most one-dimensional HIPs are easy for users to solve.  However, there is a significant decrease in human HIP solution accuracy with the increase of the global or local warping levels.  Accuracy was also quite high across all levels of HIP recognition with thin arcs in the foreground.  Adding intersecting thick arcs caused significant performance decrements, but non-intersecting thick arcs did not.

OUTLINE  Introduction  Definitions  User Study I  User Study II  Conclusion  References

References 1.Simard PY, Szeliski R, Benaloh J, Couvreur J, and Calinov I (2003), “Using Character Recognition and Segmentation to Tell Computers from Humans,”International Conference on Document Analysis and Recognition (ICDAR), IEEE Computer Society, pp , Chellapilla K., and Simard P., “Using Machine Learning to Break Visual Human Interaction Proofs (HIPs),” Advances in Neural Information Processing Systems 17, Neural Information Processing Systems (NIPS’2004), MIT Press. 3.Turing AM (1950), “Computing Machinery and Intelligence,” Mind, vol. 59, no. 236, pp Von Ahn L, Blum M, and Langford J. (2004) “Telling Computers and Humans Apart (Automatically) or How Lazy Cryptographers do AI.” Comm. of the ACM,47(2): First Workshop on Human Interactive Proofs, Palo Alto, CA, January Von Ahn L, Blum M, and Langford J, The Captcha Project.

References 7.Mori G, Malik J (2003), “Recognizing Objects in Adversarial Clutter: Breaking a Visual CAPTCHA,” Proceedings of the Computer Vision and Pattern Recognition (CVPR) Conference, IEEE Computer Society, vol.1, pages:I I-141, June 18-20, Chew, M. and Baird, H. S. (2003), “BaffleText: a Human Interactive Proof,” Proc., 10th IS&T/SPIE Document Recognition & Retrieval Conf., Santa Clara, CA, Jan Simard, P.,Y., Steinkraus, D., Platt, J. (2003) “Best Practice for Convolutional Neural Networks Applied to Visual Document Analysis,” International Conference on Document Analysis and Recognition (ICDAR), IEEE Computer Society, Los Alamitos, pp , Selfridge, O.G. (1959). Pandemonium: A paradigm for learning. In Symposium in the mechanization of thought process (pp ). London: HM Stationery Office. 11.Pelli, D. G., Burns, C. W., Farrell, B., & Moore, D. C, “Identifying letters.” (accepted) Vision Research. 12.Goodman J. and Rounthwaite R., “Stopping Outgoing Spam,” Proc. of the 5th ACM conf. on Electronic commerce, New York, NY