1. ACKNOWLEDGEMENT
I would like to express my sincere gratitude and appreciation to everyone who
made this seminar report possible. Most of all, I would like to thank my Seminar
Supervisor, Mr. Amit Kumar Jaiswal, Assistant Professor, Department of Computer
Science and Engineering, Ideal Institute of Technology Ghaziabad and Ms. Sumita
Verma, Lecturer, Department of Computer Science and Engineering, Ideal Institute
of Technology Ghaziabad, for their guidance in the seminar. With their knowledge
and experience, they guided me to successfully achieve my seminar objective.
I sincerely extend my thanks to, Dr. G. P. Govil, (Prof.) and Dr. Sudhir
Dawra, (Associate Prof. & Head) Department of Computer Science and Engineering,
Ideal Institute of Technology Ghaziabad, Uttar Pradesh for their encouragement and
support.
I express my sincere thanks to all my friends, my well-wishers and classmates
for their support and help during the seminar report.
ABHIMANYU SOOD
Roll No. 0902810002
B. Tech. (CSE)
3rd Year (A)
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2. ABSTRACT
We introduce captcha, an automated test that humans can pass, but current
computer programs cannot pass: any program that has high success over a captcha
can be used to solve an unsolved Artificial Intelligence (AI) problem. We provide
several novel constructions of captchas. Since captchas have many applications in
practical security, our approach introduces a new class of hard problems that can be
exploited for security purposes. Much like research in cryptography has had a
positive impact on algorithms for factoring and discrete log, we hope that the use of
hard AI problems for security purposes allows us to advance the field of Artificial
Intelligence. We introduce two families of AI problems that can be used to construct
captchas and we show that solutions to such problems can be used for steganographic
communication. Captchas based on these AI problem families, then, imply a win-win
situation: either the problems remain unsolved and there is a way to differentiate
humans from computers, or the problems are solved and there is a way to
communicate covertly on some channels.
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3. CONTENTS
Certificate
Acknowledgement --------------------------------------------------------------
i
Abstract -------------------------------------------------------------------------
ii
Content -------------------------------------------------------------------------
iii
List of Figures------------------------------------------------------------------
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1. INTRODUCTION --------------------------------------------------------------------- 1
2. TYPES OF CAPTCHAS ------------------------------------------------------------- 5
3. APPLICATION ----------------------------------------------------------------------- 12
4. CONSTRUCTING CAPTCHA -----------------------------------------------------
15
5. BREAKING OF CAPTCHA --------------------------------------------------------
24
6. ISSUES WITH CAPTCHA --------------------------------------------------------- 30
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4. Conclusion ------------------------------------------------------------------- 33
Reference ---------------------------------------------------------------------
34
List of Figures
1. Fig 2.1 Gimpy CAPTCHA ------------------------------------------------------------
6
2. Fig 2.2 Yahoo’s Ez – Gimpy CAPTCHA -------------------------------------------
6
3. Fig 2.3 BaffleText examples ----------------------------------------------------------
7
4. Fig 2.4 MSN Passport CAPTCHA ---------------------------------------------------
7
5. Fig 2.5 Bongo CAPTCHA ------------------------------------------------------------
8
6. Fig 2.6 First line shows ---------------------------------------------------------------
11
7. Fig 5.1 Breaking CAPTCHAs -------------------------------------------------------
27
8. Fig 6.1 Usability issues in text based CAPTCHAs -------------------------------
30
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