A seminar of CAPTCHA /* A very kind request to the viewers, please don't try to download it and just edit the name. Just take the idea from the presentation and add your innovation to it */ I hope it will be helpful to you all :) Good Luck :)

1. CAPTCHA Telling Humans and Computers Apart Automatically Presented by: Preetam Kajal Rout

2. Definition History Application of CAPTCHA Types of CAPTCHA Breaking CAPTCHA Reference Agenda

3. CAPTCHA (Completely Automated Public Turing Test To Tell Computers and Humans Apart). The P for Public means that the code and the data used by a CAPTCHA should be publicly available. T for “Turing Test to Tell” is because CAPTCHAs are like Turing Tests. What is CAPTCHA??

4. CAPTCHA is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown below, but current computer programs can't. What is CAPTCHA?? Continues…

6. Preventing Comment Spam in Blogs. Protecting website registration. Protecting email addresses from scrapers. Online Polls. Preventing dictionary attacks. Application of CAPTCHA

8. ReCAPTCHA

11. Then renders a distorted image containing the words.

12. Then presents a test to its user, which consists of the distorted image and the directions: “type three words appearing in the image.”Type three words appearing in the image.

13. Some Screenshots ofText Based CAPTCHA Pictures of CAPTCHA implemented by some popular websites.

15. It displays two series of blocks, the left and the right. The blocks in the left series differ from those in the right, and the user must find the characteristic that sets them apart.

16. After seeing the two series of blocks, the user is presented with a single block and is asked to determine whether this block belongs to the left series or to the right.To which side does the block on the bottom belong?

17. Some Screenshots of Graphics Based CAPTCHA GIMPY CAPTCHA b. PIX CAPTCHA

18. The program picks a word or a sequence of numbers at random, renders the word or the numbers into a sound clip and distorts the sound clip. It then presents the distorted sound clip to the user and asks users to enter its contents. This CAPTCHA is based on the difference in ability between humans and computers in recognizing spoken language. Audio Based CAPTCHA

20. Wikipedia(http://en.wikipedia.org/CAPTCHA) Carnegie Mellon School of Computer Science Web site (http://www.captcha.net) “Telling Humans and Computers Apart” by Luis von Ahn and colleagues. Xerox Palo Alto Research Center (http://www2.parc.com/ istl/projects/captcha/) References

21. THANK YOU !!!

22. ANY QUERIES ???