Semantic annotation or tagging of images can greatly improve the accuracy and they find the task of image annotation boring and laborious despites its benefits in terms of search and retrieval. In this paper, we introduce a novel approach of luring users into image annotation: by embedding image annotation into a CAPTCHA design. A CAPTCHA is a standard security mechanism used by popular commercial websites to prevent automated programs from abusing the online services. Millions of users solve CAPTCHA s daily in order to access web content and services. We aim to utilize human effort spent in solving the CAPTCHA into a productive work of image annotation. We introduce iCAPTCHA, a user friendly and productive CAPTCHA design. Our premise is based on the human ability to recognize images and label them in proper categories. Each time a user solves an iCAPTCHA, he/she is helping to label images in proper categories which will in turn improve image search and retrieval. using image processing to decode CAPTCHA tests, recently techniques have been developed for utilizing a 3rd party human user to break given CAPCHA s. This type of attack is particularly difficult to prevent, and our research shows that no effective solutions currently exist. One of the primary aims of this paper is to present a novel and effective method for coping with this security challenge.

1. iCAPTCHAiCAPTCHA

3. CAPTCHA AND iCAPTCHACAPTCHA AND iCAPTCHA
TECHNOLOGYTECHNOLOGY
 CAPTCHACAPTCHA (Completely Automated Public Turing
Test to Tell Computers and Humans Apart)
i. Standard security mechanism.
ii. Prevent attack of automatic scripts.
 iCAPTCHA (Interactive Completely Automated
Public Turing Test to Tell Computers and Humans
Apart)
1. next generation of CAPTCHA
2. against 3rd party human attacks( legitimate user or not).

4. Welcome to the CAPTCHA worldWelcome to the CAPTCHA world

5. CAPTCHACAPTCHA
 Simple test , easy for humans . But difficult forSimple test , easy for humans . But difficult for
computers to solve.computers to solve.
 Protect resource from attack by the use ofProtect resource from attack by the use of
timing values.timing values.
 Unable to distinguish between human attackerUnable to distinguish between human attacker
and a legitimate user.and a legitimate user.
 ApplicationsApplications
face-book ,e-mail services.face-book ,e-mail services.

6. IMCA( Instant MessengerIMCA( Instant Messenger
CAPTCHA Attack )CAPTCHA Attack ) System used in CAPTCHA.System used in CAPTCHA.
 Instant Messenger (IM) network .Instant Messenger (IM) network .
 IM allow communication between two or moreIM allow communication between two or more
participants over a network .participants over a network .
 Data exchange .Data exchange .
 IMCA ComponentsIMCA Components
 Attack script : custom made to attackAttack script : custom made to attack
 IM connector : send and receive instantIM connector : send and receive instant
messagesmessages

7. EXAMPLE FOR CAPTCHAEXAMPLE FOR CAPTCHA

8. iCAPTCHA ( InteractiveiCAPTCHA ( Interactive
CAPTCHACAPTCHA))
 Reliable technique.Reliable technique.
 Concept and implementationConcept and implementation
a)a) use sequence of mouse clicks.use sequence of mouse clicks.
b)b) first click -CAPTCHA image creating.first click -CAPTCHA image creating.
c)c) mouse click- iCAPTCHA input.mouse click- iCAPTCHA input.
d)d) correct – perform functions.correct – perform functions.

9. iCAPTCHA MechanismiCAPTCHA Mechanism

10. interactioninteraction
Legitimate
Web Server
User
1..Download CAPTCHA
Challenge
2.. Response to
CAPTCHA
Fig. Legitimate user’s interaction with iCAPTCHA

11. CAPTCHA in different searchCAPTCHA in different search
engineengine

12. Security FeaturesSecurity Features
• CAPTCHA - time out value measuring .CAPTCHA - time out value measuring .
( not detect legitimate user or not .)( not detect legitimate user or not .)
• iCAPTCHA - time out value measuring periCAPTCHA - time out value measuring per
character.character.
( detect legitimate user or not .)( detect legitimate user or not .)

13. Attack Detection AlgorithmsAttack Detection Algorithms
Algorithms:Algorithms:
1.1. single slow response detection algorithmsingle slow response detection algorithm
2.2. two consecutive slow response algorithmtwo consecutive slow response algorithm
3.3. dynamic detection threshold algorithmdynamic detection threshold algorithm

14. LIMITATIONSLIMITATIONS
 users with impaired vision or motor skills.users with impaired vision or motor skills.
 iCAPTCHA performance against characteriCAPTCHA performance against character
recognition based attacks.recognition based attacks.

15. CONCLUSIONCONCLUSION
 protecting resources from attacks.protecting resources from attacks.
 provide statistical timing for evaluating theprovide statistical timing for evaluating the
mechanism.mechanism.
 attack detection based on detection algorithms.attack detection based on detection algorithms.
 we hope iCAPTCHA encourage researches andwe hope iCAPTCHA encourage researches and
develop more secure and reliable CAPTCHA.develop more secure and reliable CAPTCHA.

16. THANK YOU...THANK YOU...