

The Next Big Thing in CAPTCHAs - edw519
http://www.catchmyfame.com/2009/10/14/the-next-big-thing-in-captchas/

======
felixc
This looks trivial to defeat by simply comparing the top and bottom edges of
each image, and picking the combination with the best fit. The faces might
fare a little better under that test, but the logos and colourful shapes would
likely be successfully matched every single time.

~~~
mukyu
Actually, logos are the harder of the pair. My simple attempt only gets around
90% success because some of the logo pieces have a group of white at the top
and bottom. This makes it so the bottom piece of a logo and the top piece of
the logo make good fits for the middle and bottom rows. Example from my
solver: <http://imgur.com/CQvcH.png>

The photos take up the entire frame with various colors instead of one solid
one, so it is not likely for any of them to end up with a mismatch like this.

~~~
felixc
Oh, that's a really interesting case! I hadn't seen any like that when I
posted, but that's definitely something to consider. I think you could work
around whenever you get multiple "perfect" fits like that by comparing a)
whether they are non-blank, or, more sophisticated, b) are there continuous
edges across the boundary.

------
daeken
Broken: <http://pastie.org/656332>

Naive attack, but it works well in my testing (ran it about 10 times, 100%
success rate). If you have PIL installed, just run it through python and it'll
grab an image and print whether it succeeded or failed to verify its solution.

~~~
jcl
Or a Greasemonkey script: <http://pastie.org/656481>

(Adds a "Solve" link that moves the image rows into a solved position. Tested
in Firefox 3.5.)

------
dctoedt
Slightly off topic: The bag-of-potatoes puzzle could trip some people up.

The stated problem is: “You have a 100 pound bag of potatoes. 99% of the bag
is water weight. You leave the bag in the sun for a few hours. Now you bring
it in and it is only 98% water weight, due to evaporation. What is the new
total weight of the bag of potatoes?”

The first-reaction answer is that the bag now weighs 98 pounds. But originally
the bag contained 1 lb of solid, 99 pounds of water. (Let's assume no other
liquids than water). After evaporation, you still have 1 lb of solid, but it's
now 2% of the total weight. For 1 pound of solid to equal 2% of total weight,
the total weight has to be 50 pounds. That means the bag has only 49 pounds of
water remaining. (That seems like a lot of evaporation for just a few hours in
the sun.)

~~~
pavel_lishin
I don't understand how you reached the conclusion that the 1lb of solid
becomes 2% of the total weight after evaporation.

Seems to me that it would be 1.01%.

~~~
dctoedt
The statement of the problem says that, after evaporation, the bag is now 98%
water by weight, meaning that the solid matter is now 2% (100% - 98%) instead
of the 1% it started out as.

Per the problem statement, the 100-pound bag was initially 99% = 99 pounds of
water. The non-water part (which we'll assume for simplicity was non-volatile
solids) was therefore 100 pounds - 99 pounds = 1 pound. Solids don't
evaporate, so even after evaporation, the 1 pound of solid matter remains.
That 1 pound is now 2% = 1/50 of the weight, per above. The total weight after
evaporation is therefore 50 pounds.

~~~
pavel_lishin
Ah, I see. I'm slow.

------
ggrot
Problems:

\- Easier to defeat than OCR.

\- Only 9 combinations, so random guessing works fine too.

\- Visually impaired fail.

~~~
pavel_lishin
\- Utterly dependent on a mouse. This is annoying.

~~~
joshfinnie
reliance on javascript

~~~
tomjen2
I don't think that is a failure though - that alone removes a lot of bots.

------
chanux
Or may be this is the next big thing. ;) <http://www.makeuseof.com/tech-
fun/break-this-captcha/>

------
Dilpil
Captcha is futile as a way to prevent people spamming, but a great way to push
funding for emerging areas in Computer Science. I recommend we go with image
edge detection next.

------
jonknee
It's safe to say the author has no concept of how sophisticated CAPTCHA
breakers are these days. This would last about five minutes on Gmail before
being cracked.

------
dctoedt
Money-motivated "arms races" like this might well be a driver for the
evolution of technologies that, collectively, could be called "artificial
intelligence." (This thought probably isn't original to me, but I can't think
of where I might have read it.)

------
toto
I doubt solving a puzzle is a good idea for the conversation rate. It would be
interesting to see some A/B testing results...

~~~
tomjen2
It is much more fun than a captcha.

------
swombat
Heh, the article has been pulled.

------
bhseo
The next big thing in turning visitors away.

