Captcha

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Captcha

  1. 1. CAPTCHA A CAPTCHA is a type of challenge – response Test that response is generated by a human being or computerCAPTCHA – Completely Automated Public Turing test to tell Computers &Humans Apart.
  2. 2. Why captcha was needed? Online Polls Protecting Web Registration E–Ticketing Email Spam
  3. 3. Turing Test :- To test a machine’s level of intelligence CAPTCHA employs a reverse Turing testjudge = CAPTCHA programparticipant = userif user passes CAPTCHA, he is humanif user fails , it is a machine
  4. 4. Types of CAPTCHAs :-Texts CAPTCHAsGimpyEz – GimpyMSNs Passport Service CAPTCHAsAudio CAPTCHAs
  5. 5. Texts CAPTCHAs :-Simple, normal questions like: What is twenty minus three? What is the third letter in UNIVERSITY? If yesterday was a Sunday, what is today?
  6. 6. Gimpy :- Designed by Yahoo & CMU(Carnegie Mellon University) Picks up 10 random words from dictionary, and displayingthem in a distorted and overlapped manner. User has to recognize at least 3 words. If the user is correct, then he is admitted.
  7. 7. Ez – Gimpy :- A modified version of Gimpy. Yahoo used this version in Messenger. Randomly picks a single word from a dictionary and appliesdistortion to the text.
  8. 8. MSNs Passport Service CAPTCHAs :- Provided for Microsoft’s MSN services. Eight characters(upper case) and digits. Warping is used to distort. Very strong implementation, hasn’t been broken.XTNM5YRE L9D28229B
  9. 9. Audio CAPTCHAs :- Consists of downloadable audio clip. User listens & enters the spoken word. Google’s audio enabled CAPTCHA
  10. 10. reCAPTCHA :-Used in Google books project.Two words are shown, the program knows the first word.If the user enter the first word correctly, it assumes that the second unknownword will also be entered correctly.
  11. 11. API Key for reCAPTCHA:- Login www.recaptcha.net with your Gmail account. Domain Name – localhost.com It will generate public key and private key Public Key: 6LfAIuASAABBBAl2TAmrFWlGUQyols8bqcVvI1c6Use this in the JavaScript code that is served to your users Private Key: 6LfAIuASAABBBFHNHH--MitbQPqnezzg3XftrX5kUse this when communicating between your server and our server. Besure to keep it a secret. https://developers.google.com/recaptcha/docs/display

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