In 1999, slashdot.com create an online
poll to ask the people which graduate school had the best computer
science program. This was a big mistake. Both MIT and Carnegie Mellon
wrote programs or “bots” that voted for them. As a result the
poll became a contest between the voting “bots” where each school
ended up with over 20,000 votes while the rest had less than a 1,000
votes. This led to research in preventing such programs and the
CAPTCHA was created. CAPTCHA stands for “Completely Automated
Public Turing Test to Tell Computers and Humans Apart.” The idea is
that the CAPTCHA is a test that humans can pass but computers can't
pass with a probability greater than guessing. What does the CAPTCHA
have to do with computer image processing?
CAPTCHAs are distorted images which
computers can't solve due to the segmentation problem. Computers are
actually better than humans at solving fundamental CAPTCHA problems.
Yet the computers fail at separating letters from each other,
recognizing distorted letters, and understanding the context of each
letter. Humans on the other hand excel at recognizing the letters and
the resulting words. Computers are not able to recognize distorted
letters because there are infinitely many distortions. They are not
able to separate letters from each other as well because CAPTCHA
images have lines going across the words and confusing background
patterns. Thus the computer's CAPTCHA image processing problem is a
difficult problem in the field of artificial intelligence. One last
interesting thought: CAPTCHA is a program that can generate and grade
tests that it itself cannot pass.
Sources:
Information Security: Principles and Practice by Mark Stamp
Interesting post, I have always found CAPTCHAs very strange. I was always very curious about how the computer is able to spit out all of these randomized pictures. Do you happen to know why I am still able to post this comment even when I only fill in the CAPTCHA from only one of the two pictures? also, Wikipedia is generally not considered kosher siting material.
ReplyDeleteIt is really interesting to read your post. I have seen CAPTCHAs everywhere, and have been wondering what they truly are and how they are created. Thanks to your post, now I know what they originally were created for. However, sometimes I feel like it is very hard to type provided letters in CAPTCHAs since the letters are blurry and hard to see. Your post is informative; however, you could improve it more by providing more images.
ReplyDeletehello, sander. it's excited post. sometimes, I can't figure it out what is that letter in CAPTCHAs. and Sometimes, it doesn't work on mobile page and voice function. it is good for security but it sometimes tired work. I think this tech should improve more. But it's really good idea to protect auto-filling. Your post is very informative one and good to know how it is created.
ReplyDeleteHi Sander,
ReplyDeleteIt is an interesting topic. You have organized your post very well. I liked the way you have explained by giving a problem real scenario and CAPTCHA as a solution for it. The image you have added supports the content of the post. In the second paragraph you have discussed about uses and problems in CAPTCHA. Humans can read distorted images whereas computers cannot read them. This is the core idea behind CAPTCHA.
Overall, it is a good post!
Great post. This was really interesting I had never heard the source of a CAPTCHA even though I see them all the time, and will have to use one to post this comment. It is incredibly ironic that the machines create CAPTCHAs which they cannot solve.
ReplyDelete