E-commerce services are suffering abuse by programs (bots, spiders, etc.) which masquerade as legitimate human users.  Efforts to defend against such attacks have, over the last few years, stimulated the investigation of a new family of security protocols -- "Human Interactive Proofs" (HIPs) -- which allow a person to authenticate herself as a member of a given group: e.g. as human (vs. machine), as herself (vs. anyone else), as an adult (vs. a child), etc.  The vast majority of commercial uses of HIPs today are CAPTCHAs -- "Completely Automatic Public Turing tests to tell Computers and Humans Apart" -- which exploit the gap in ability between humans and machine vision systems in reading images of text.  HIP challenges can also be non-graphical, e.g., requiring recognition of speech, solving puzzles, etc.

Since the First Workshop on Human Interactive Proofs in January 2002, the use of CAPTCHAs has risen rapidly worldwide and awareness of HIPs has spread through many articles in the scientific and general press.  UC Berkeley has broken the Yahoo/CMU EZ-Gimpy CAPTCHA.  Microsoft Research, PARC, and Lehigh University have developed new generations of reading-based CAPTCHAs.  CAPTCHAs have emerged as a front-line defense against spam.  Many new applications are emerging.

This workshop will bring together researchers, engineers, and users of HIPs and CAPTCHAs to review the state of the art, discuss recent technical and commercial progress, identify pressing technical and business challenges, and to plan next steps for the field.


Submissions are invited on these and related topics:

• Descriptions of innovative HIP and CAPTCHA theory, technology, and systems.
• Methods for locating "ability gaps" (families of tasks on which humans perform better than machines).
• Perceptual & cognitive modalities for HIPs:  visual, auditory, inferential, etc.
• Measuring and controlling the difficulty of CAPTCHAs for both humans and machines.
• Generating large numbers of distinct HIP challenges.
• Detecting CAPTCHA break-in.
  
• User studies of CAPTCHAs:  reliability, ease of use, "friendliness," etc.
• Novel CAPTCHA applications and business cases.
  
• Related results from the fields of security/cryptography, computer vision, document image analysis, cognitive science & psychophysics, law, business, etc.
  
• Proposals for benchmarks and systematic attacks on published CAPTCHAs.
• Critical surveys of the state of the art of HIPs and CAPTCHAs.

We invite two classes of submissions:
1. Regular Paper (for researchers and professional practitioners): full-length papers, refereed, published in the workshop proceedings, long presentation.
Deadlines for regular papers:

January 15	Submission of manuscripts
February 15	Acceptance notification
March 15	Camera-ready copy due

2. Abstract of Remarks (for businesspeople, end-users, students): short papers (1-5 pages), not refereed, distributed at the workshop but otherwise unpublished, brief presentation.
Deadlines for abstracts of remarks: 

March 15	Submission of abstracts
April 1	Acceptance notification