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Are you Human?

Are you Human?. What is CAPTCHA?. C ompletely A utomated P ublic T uring test to tell C omputers and H umans A part It uses a type of challenge-response test to determine that the response is not generated by a computer.

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Are you Human?

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  1. Are you Human?

  2. What is CAPTCHA? • Completely Automated Public Turing test to tell Computers and Humans Apart • It uses a type of challenge-response test to determine that the response is not generated by a computer. • The goal: To create an automated test that is easy for a human to pass but difficult for a computer

  3. Turing Test „Standard Interpretation" player C, the interrogator, is tasked with trying to determine which player - A or B - is a computer and which is a human. Reverse Turing Test A CAPTCHA is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human.

  4. Background • CAPTCHAs are based on open AI problems • Breaking CAPTCHAs help advance AI by solving these open problems • Improving CAPTCHAs help telling computers and human apart • Win-win situation

  5. Applications • Preventing Comment Spam in Blogs. • Online Polls. You cannot trust the results of an online roll because anybody could just write a program to vote for their favorite option thousands of times. • Protecting Website/E-mail Registration • Preventing Dictionary Attacks (in password systems). Prevent a computer to iterate through the entire space of passwords by requiring it to solve a CAPTCHA after a certain number of unsuccessful logins.

  6. Types of CAPTCHAs • Text based • Gimpy, ez-gimpy • Gimpy-r, Google CAPTCHA • Simard’s HIP (MSN) • Graphic based • Bongo • Pix • Audio based • Simple Math based

  7. Breaking CAPTCHAs • Most text based CAPTCHAs have been broken by software (OCR) • Using cheap human labor to process the tests (sweatshops). • Insecure implementation that allow the attacker to completely bypass the CAPTCHA

  8. reCAPTCHA • New form of CAPTCHA that also helps digitize books • The words displayed to the user come directly from old books that are being digitized and OCR could not identify • Pairs an unknown word with a known one • Distorts them both and puts a line through them and then sent them to be proofread • Respondent answers both elements: • half of effort validates the challenge • the other half is captured as work

  9. No CAPTCHA reCAPTCHA(by Google)

  10. Thank you!

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