Securing passwords against dictionary attacks
Proceedings of the 9th ACM conference on Computer and communications security
Defending against an Internet-based attack on the physical world
Proceedings of the 2002 ACM workshop on Privacy in the Electronic Society
A new privacy model for hiding group interests while accessing the Web
Proceedings of the 2002 ACM workshop on Privacy in the Electronic Society
Human Interactive Proofs and Document Image Analysis
DAS '02 Proceedings of the 5th International Workshop on Document Analysis Systems V
MULTIMEDIA '03 Proceedings of the eleventh ACM international conference on Multimedia
Telling humans and computers apart automatically
Communications of the ACM - Information cities
Defending against an Internet-based attack on the physical world
ACM Transactions on Internet Technology (TOIT)
Preventing bots from playing online games
Computers in Entertainment (CIE) - Theoretical and Practical Computer Applications in Entertainment
ScatterType: A Legible but Hard-to-Segment CAPTCHA
ICDAR '05 Proceedings of the Eighth International Conference on Document Analysis and Recognition
A Human Interactive Proof Algorithm Using Handwriting Recognition
ICDAR '05 Proceedings of the Eighth International Conference on Document Analysis and Recognition
Proceedings of the 4th ACM workshop on Recurring malcode
Botz-4-sale: surviving organized DDoS attacks that mimic flash crowds
NSDI'05 Proceedings of the 2nd conference on Symposium on Networked Systems Design & Implementation - Volume 2
Embedded noninteractive continuous bot detection
Computers in Entertainment (CIE) - Theoretical and Practical Computer Applications in Entertainment
Avoiding Massive Automated Voting in Internet Polls
Electronic Notes in Theoretical Computer Science (ENTCS)
Synthetic handwritten CAPTCHAs
Pattern Recognition
Proceedings of the 2nd ACM workshop on Security and artificial intelligence
CAPTCHA: using hard AI problems for security
EUROCRYPT'03 Proceedings of the 22nd international conference on Theory and applications of cryptographic techniques
An efficient segmentation algorithm for CAPTCHAs with line cluttering and character warping
Multimedia Tools and Applications
Heliza: talking dirty to the attackers
Journal in Computer Virology
OTM'06 Proceedings of the 2006 international conference on On the Move to Meaningful Internet Systems: AWeSOMe, CAMS, COMINF, IS, KSinBIT, MIOS-CIAO, MONET - Volume Part I
Building segmentation based human-friendly human interaction proofs (HIPs)
HIP'05 Proceedings of the Second international conference on Human Interactive Proofs
A highly legible CAPTCHA that resists segmentation attacks
HIP'05 Proceedings of the Second international conference on Human Interactive Proofs
Visual CAPTCHA with handwritten image analysis
HIP'05 Proceedings of the Second international conference on Human Interactive Proofs
Leveraging the CAPTCHA problem
HIP'05 Proceedings of the Second international conference on Human Interactive Proofs
Protection through Intelligent and Multimedia Captchas
International Journal of Adaptive, Resilient and Autonomic Systems
A new CAPTCHA interface design for mobile devices
AUIC '11 Proceedings of the Twelfth Australasian User Interface Conference - Volume 117
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Abstract: We exploit the gap in ability between human and machine vision systems to craft a family of automatic challenges that tell human and machine users apart via graphical interfaces including Internet browsers. Turing proposed [Tur50] a method whereby human judges might validate "artificial intelligence" by failing to distinguish between human and machine interlocutors. Stimulated by the "chat room problem" posed by Udi Manber of Yahoo!, and influenced by the CAPTCHA project [BAL00] of Manuel Blum et al of Carnegie-Mellon Univ., we propose a variant of the Turing test using pessimal print: that is, low-quality images of machine-printed text synthesized pseudo-randomly over certain ranges of words, typefaces, and image degradations. We show experimentally that judicious choice of these ranges can ensure that the images are legible to human readers but illegible to several of the best present- day optical character recognition (OCR) machines. Our approach is motivated by a decade of research on performance evaluation of OCR machines [RJN96,RNN99] and on quantitative stochastic models of document image quality [Bai92,Kan96]. The slow pace of evolution of OCR and other species of machine vision over many decades [NS96,Pav00] suggests that pessimal print will defy automated attack for many years. Applications include 'bot' barriers and database rationing.