Sample Captcha
Pictcha is an experiment designed to improve security over typical text-based CAPTCHAs and enhance image search.
CAPTCHA is an acronym for completely automated public turing test to tell computers and people apart. It ensures that an online transaction is being performed by a human rather than a computer.CAPTCHAs have been successfully used to distinguish people from computers by challenging users to decipher distorted text, a task that is relative easy for people but quite difficult for computers.
However, with the improvement of machine-learning algorithms, CAPTCHAs must be regularly updated to thwart would-be spammers.
Sample Recaptcha
Thus came the concept of ReCaptcha.About 200 million CAPTCHAs are solved by humans around the world every day. In each case, roughly ten seconds of human time are being spent. Individually, that’s not a lot of time, but in aggregate these little puzzles consume more than 150,000 hours of work each day. What if we could make positive use of this human effort? reCAPTCHA does exactly that by channeling the effort spent solving CAPTCHAs online into “reading” books.
In the Pictcha experiment, users are shown a randomly selected Web image and challenge them to provide two descriptive labels.Passing the test requires that at least one of the user-provided labels matches a known tag for the image. The collection of known tags is generated by previous users who have tagged the same image.Pictcha is currently in experiment stage.
Try a Pictcha demo here
Tags: Anti-spam, CAPTCHA, Computer security, E-mail, E-mail spam, Human-based computation, image search, PICTCHA, Spamming, Technology/Internet, Web 2.0
There are a couple of things wrong there. The “pictcha” is suggesting 3 valid answers. That makes the probability of a bot getting the answer right – 33%. This is HUGE ! I wrote a list of other captcha techniques and why they are good / bad. Check it out if it interests you
Your statistics knowledge is probably the worst. You dont event know how to calculate probability:
probability to select 1 4-char word = A(4,28), for 5-char word= A(5,28), so on.. the rest for you to think of.
Did you even go through the application ? The app actually suggests 3 possible answers to the user (It does not seem to do so anymore). Selecting one of the three answers is easy for a computer program. You dont have to type a N char word when the words are already presented to you. Try the application before you hail yourself as a ‘probability guru’
Hi CertPal i think although probability says its guessing possibility 33% but its nearly impossible to guess for a computer what it is until and unless a photo search algorithm is developed orwe name the photo.
I agree that a computer will have to make some sort of intelligent picture recognition before attempting to pick one of the 3 answers. But if you know one of the three choices being presented is correct, why would you even bother. Pick one randomly and a bot should be able to submit spam.
They seem to have corrected the problem by not suggesting answers anymore. Picture captchas are harder to get right as trans has suggested in his comment below.
It a good idea, but some obvious tags didn’t fly. Like the picture of bicycles. “Bike” failed.
Thats right. It is a self learning algorithm. For each word you put the Pictcha becomes stronger
Excellent post, how can I subscribe to this?
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