# Croatian brainboxes deploy calculus-based CAPTCHA

Boffins at Croatia's Ruđer Bošković Institute are confronting surfers with difficult maths problems as an alternative to conventional CAPTCHA conundrums. Web users signing up for new accounts are typically asked to decipher the text in a jumbled up image and input the results into a dialogue box. The challenge-response test is …

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I recall a story from the 80's, where an Eastern European student union wanted to keep the secret police out of their club rooms, so they instituted a password challenge: "What is the derivative of x squared?". After a while, the secret police figured out that "2x" got them in, so the student union changed the question to "What is the derivative of y squared?". Which worked.

2. #### My title is Mr.

But the expression contains only the single variable, x, so why a partial derivative?

3. #### The first one is easier

The first captcha is easier (as long as you can remember operator precedence).

And it says:

"Note: If you do not know the answer to this question,

reload the page and you'll (probably) get another, easier, question."

If you reload, then you start getting calculus.

4. #### And I thought

working in IT, I would never get to use my Physics Degree....

5. #### easy, its 20

although it looks a little daunting, its a really easy case, sin goes to cosine, and its evaluated at x=2pi. cosine of any multiple of 2pi is 1.

therefore its just a case of getting the front number 4 x 5 - as d/dx of Asin(mx) = Am cos(mx)

1. #### I think you mean...

it was easy, 20 years ago!

6. #### I cant answer that..

I'm obviously not human!

Dammit, been found out.

Beep - Destroy all humans - Beep.

7. #### Heh, that reminds me of.

http://bash.org/?43366

8. #### I suppose it could keep idiots out too.

Win-Win.

Someone should just hurry up and implement a Voight-Kampff though, job done.

1. #### Nice!

So someone who doesn't understand calculus or advanced math is an idiot then? Some of the world best artists, photographers, campaigners for world peace, etc are just lumped in with 90% of the world's population who would have to spend 10 mins to fathom out that question before even attempting an answer?

Granted most of us would not be knocking on the door of an academic research institute but it's good to see academic snobbery alive and well on the Reg!

1. #### Touchy today?

"So someone who doesn't understand calculus or advanced math is an idiot then? "

Artists, peace campaigners and any body else attempting to join a Croatian advanced math club without a good knowledge of advanced math is probably an idiot, yes.

2. #### Actually...

"So someone who doesn't understand calculus or advanced math is an idiot then?"

Well, calculus is 300 years old, and is not exactly advanced maths -- it's fundamental and basic -- and it's the numerical equivalent of knowing who Tennyson is. In the UK at least (and I assume the US), knowing anything other than basic arithmetic (i.e., adding and multiplying single-digit numbers) is considered advanced, and this is generally innumerate people's way of trying to cover up the fact that they have a severe and gaping hole in their education.

To see what I mean, replace "can't add up" with "can't read". People who can't read in the UK are either three or are considered mentally retarded, but people who cannot do arithmetic are just "not good with numbers", despite arguably arithmetic being a much more natural thing than language.

Maybe this calculus problem, which actually is a fairly easy calculus problem (differentiation is a science, integration is an art) is an unreasonable captcha, but this post smacks of society's general belief that mathsy stuff is hard and dull, etc..

(On a totally unrelated point, I remember getting one of these captchas ages ago for some forum, but I cannot remember which one...)

1. #### Only 300? Young'uns

Calculus may be 300 years old, but arithmetic is much, much older. Not knowing calculus is hardly the same as "can't add up" A person who can't distinguish between arithmetic and calculus is in no position to lecture on comparisons with "can't read".

1. #### I hope this catches on

Physicists putting up X-ray diffraction challenges, biologists making you work out the species from a DNA sequence (all of it) and the geologists just threatening to take a hammer to your tender bits.

2. #### I guess I should refine my comment

Basic arithmetic = learning the alphabet.

More advanced arithmetic = learning to spell, read up to an 11 year old's level.

Basic geometry = reading a few books.

(If you actually think about it, that's about when people do it in school! However, it seems OK to people to forget the right-hand side, but not the left-hand side.)

Back to your comment, I compared calculus to Tennyson, not reading. I later went on to say that not being able to do arithmetic is equivalent to to not being able to read. I moved away from the actual calculus point and on to generally bemoaning a society that considers anything numerical to be nerdy and uncool; this is really not going to help us in the coming, totally technological, reality.

3. #### re: Nice!

Actually makes sense. Yes I'd be firmly in the "idiot" camp on this one having had no desire to pursue calculus beyond what was strictly required of me (and even that turned out to be a complete waste of time based on precisely zero uses of that knowledge in the last 20 years), but let's face it, I'm not going to ever be signing up for an account on that system, am I?

For specialist fields like this why *not* use specialist-field-related captchas? Not only would it help defeat spammers, it would also maybe help defeat the average basement-dwelling troll, too. Wouldn't be any worse than the capctha I saw recently which had accented characters in it.

Of course it all falls apart if the field involves things which are more easily processed by computers than humans anyway but at the rate things are going with some captchas it won't be long before computers are the only things which *can* decode the bloody things.

2. #### Blimey

Excellent reference!

9. #### It makes sense

If theres one thing humans are good at, that computers could never be programmed for.. I'm sure its calculus!

1. #### @James 129

Dare you to out-reduce or out-solve Maple or Mathematica. Perhaps they could just have a CAPTCHA system that asks what the current celeb-du-jour got up to recently?

1. #### re: @james 129

Your solution to non-nerds being excluded is to exclude the nerds??

Not nice.

Sincerely,

A nerd that could not tell you who the celeb-du-jour even is, let alone what they are up to.

2. #### Well

"Perhaps they could just have a CAPTCHA system that asks what the current celeb-du-jour got up to recently?"

Hang on, didn't this computer just beat(ish) a human at this sort of thing? Except, you need to say

"This is the action that the current celeb-du-jour got up to recently."

2. #### The CAPTCHA for politicians would have to be...

... based on lying. :)

(with added score for well faked sincerity)

10. #### I could not remember ...

whether Dsin is cos or -cos. (Sigh.)

1. #### ...think graphically

sine is increasing as it passes through 0, so Dsin must be +cos!

"what is the air speed veolicity of an unladen swallow"

1. #### African

or European?

12. #### To continue...

... please solve the P versus NP problem...

x = 3;

y = 71;

x ^= y;

y ^= x;

x ^= y;

What is x?

1. #### What is x?

x are what I have with bacon.

14. #### OK, so I may not understand calculus...

... but these so-called "brainboxes" don't understand CAPTCHAs. Using something that can be solved more easily by machine than by (some) humans is an epic fail.

And now on to the service they're offering: A "random" bit generator. So, then, would you rely on the ability of these pranksters to build an even remotely reliable (P)RNG for your cryptography? Yeah, right...

1. #### RTFL

"a fast non-deterministic random bit (number) generator whose randomness relies on intrinsic randomness of the quantum physical process of photonic emission in semiconductors and subsequent detection by photoelectric effect. In this process photons are detected at random, one by one independently of each other. Timing information of detected photons is used to generate random binary digits - bits."

A little more reading finds that it easily passes every test of randomness they've put it to.

15. #### re: machine processing

Maple, Mathematica, etc. are great - if you give them the problem in a form they can understand. Presented as an image, it's a good bit more challenging. Conventional captcha-solvers can stop once they've identified all the characters. This requires also parsing the correct mathematical meaning, which is sensitive to the spatial layout (e.g., 112 is different from 11^2 (11 squared = 121) and from 11_2 (11 base 2 = 3), and then solve it.

The best captchas I've seen are semantics-based, asking questions such as "what is the domain name of this site?". Answering them correctly requires understanding natural language, which is trivial for humans, but almost impossible for computers. Specialized knowledge also works well; in this case, anyone who needs truly random data has most likely studied calculus, and if necessary can look it up or ask a colleague who remembers it better.

16. #### It's a joke innit ?

And besides, while a machine can easily be programmed to solve the problem itself, it (presumably) can't resolve the captcha, as it can't process the image - which, after all, is the point of a catcha. But I do agree with Mike 140, why is the problem expressed as a partial derivative ? Or is that part of the joke ?...

Henri

17. #### being lazy..

.. I refreshed a couple of times to see just how easy a question would turn up.

My third poser was simple arithmetic along the lines of...

-2 * (-4) +7 =

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