10 ms·

Hardest captcha ever?

222 points by dalys 16y ago

moblivu 16y ago
Hardest Captcha for a human: Maybe Hardest Captcha for a machine: Not so sure ! You can just pass the equation in Wolfram Alpha directly and you have your answer! The font is crystal clear and the equation is quite simple.
pluies_public 16y ago
I thought it had to be static, but no: the captcha actually changes at each page reload. At least it will weed out the non-mathematicians easily...
- ugh 16y ago
  Hardly. You can just type it into WolframAlpha, that works perfectly. (Which is quite funny because you are letting the computer solve something that’s supposed to keep computers out.) You don’t even need to learn any fancy syntax, “derivative of” works great. (High school math homework would be so much easier with WolframAlpha.)
noamsml 16y ago
Most of these are really easy. I got a partial derivative of a constant. And honestly, if you can't answer basic math questions, you probably have no use for a quantum random bit generator.
- akie 16y ago
  and besides, I'm not entirely sure that these are "unbreakable" whatsoever. If you really want to break this, I'd do some math-specific OCR + WolframAlpha...
  - spc476 16y ago
    The image is in a clean looking font, so the OCR would probably be decent. Also, the question I got (Find the least real zero of the polynomial: p(x) = x^2 + 6x + 9) I typed, as is, into Wolfram Alpha and well, look at that, x = -3.
- tallanvor 16y ago
  I'm not sure I'd consider calculus to be a basic math question, except in the context of uses where you have a real need for this level of randomness.
  - Jach 16y ago
    <semi-sarcastic-rant />This is what [one of many things] is wrong with the educational system! Sure it's amazing that public schools have collectively taught people basic algebra (in theory), but we should set the new bar to Calculus and just keep pushing it up every so often. (I think Bayesian stats are more difficult than straight-up calculus though I'd like to see a public familiarity with both...) Calculus has been around for a pretty long time, there's plenty of good material out there to learn it and people who understand it to teach it, there's no real reason it shouldn't be required curriculum these days.
    - jmilloy 16y ago
      I would NEVER put calculus into required curriculum. Calculus is far less important than some simple number theory, logic, and the ability to think about abstract problems creatively. The tragedy is that we push towards calculus (which is really just advanced arithmetic until you get to, say college, real analysis) at the expense of these other skills.
      - HelloBeautiful 16y ago
        IMHO you don't understand Calculus good enough yourself. It's one of the most powerful tools humankind has come with. A couple of simple ideas aplicable practically everywhere.
      - Jach 16y ago
        While agreeing with the sister-child I'll also say that yes, other math and thinking skills are also important, but there's no reason we can't have those and calculus too. Throw out some of the more useless things like PE, get rid of certain requirements like art, maybe take away a year or two of the "read books most of the class doesn't care about and write essays hurriedly read over by the prof to later be never read again" English classes. Even just removing one required semester (half a year) of PE and one required semester of English (which shouldn't be very controversial) frees up two semesters, which for a high school level accommodates Calculus just fine. I'd love to see mathematical analysis courses taught at the high school level too (especially since many grown adults are under the impression math in general is like the algebra they did in high school) but that might be getting ahead of ourselves. I also don't see why you can't teach number theory et al. throughout all the math courses. I never had a formal trigonometry course because it was taught along the way.
- mrchess 16y ago
  Mine had a complex multiplication problem but had 0 as a multiplier. Can't get easier than that!
- wiredfool 16y ago
  Yep, I saw a lot of derivatives of a constant, and multiplies by zero. There were a couple that weren't obviously 0, but I wouldn't be surprised if most of the actual answers were 0.
- philh 16y ago
  I got "find the least real zero of the polynomial: -7 * 4 - 7". Somehow I doubt "mu" would be accepted. (That sort of think has only shown up once over multiple refreshes though.)
  - repsilat 16y ago
    Just to prove you are a human, please answer the following math challenge. -6 + 5 * 0 = ? (I guess I just got lucky?)
    - thret 16y ago
      I got d/dx(2sin(3pi)+0) el oh el, I suppose I got lucky also.
  - sliverstorm 16y ago
    I got that one too, and misinterpreted it as I always do and made it stupidly complex in my head. For a minute, I thought it was asking for the least real, i.e. most imaginary, zero.
makmanalp 16y ago
Ha, by this logic, a large majority of the current world population aren't humans :)
- merijnv 16y ago
  Well, to be fair the easiest captcha's are easy high school level equations and (as someone else already pointed out) if you can't solve these you have no business obtaining an account for extremely high quality quantum random numbers. (I believe they provide about 7.8 or 7.9 bits of entropy per byte)
  - nettdata 16y ago
    I'll stick with Lavarand, thanks... good enough for my needs. http://en.wikipedia.org/wiki/Lavarand http://en.wikipedia.org/wiki/Lavarand
  - pavel_lishin 16y ago
    I buy my random numbers from a guy in the alley behind my building. He says they fell off a truck.
  - HelloBeautiful 16y ago
    OMG! "extremely high quality quantum random numbers" Thats an interesting product to sell.
- nickolai 16y ago
  It's just a little more targeted than the average captcha. It should weed out both bots and people you wouldn't want using the website in the first place.
  - dhimes 16y ago
    Unless they become popular and the answers are too easy. Then you can guess the answer without even understanding the problem.
- crocowhile 16y ago
shasta 16y ago
Sounds like a great way to stock up on fake accounts submitted by people who just want to know if they got the question right
- knowtheory 16y ago
  i even made a typo in my login handle >_< got the question right though.
loudmax 16y ago
It's a reverse captcha! If you answer too quickly it knows you're a computer.
TorbjornLunde 16y ago
Isn't using math questions to stop bots(computers), a bit like trying to stop tanks with barbed wire?
mvalle 16y ago
I don't think it would be hard to do, in fact, they reverse the whole point of a CAPTCHA. A CAPTCHA is supposed to be a task that is easy for humans, but difficult for computers. High-level mathematics is difficult for humans but easy for computers. They do have some success of telling computers and humans apart, though.
- mrspeaker 16y ago
  Precisely the reason I wrote the very useful "human.txt" captcha: http://www.mrspeaker.net/2010/07/15/humans-txt/ http://www.mrspeaker.net/2010/07/15/humans-txt/ Stops those pesky humans wasting precious robot bandwidth and is quite a bit harder than the Quantum Random Bit Generator captcha ;)
  - deleted 16y ago
    [deleted]
- iy56 16y ago
  High-level mathematics is difficult for humans and provably impossible for computers.
  - timtadh 16y ago
    Correct. For those that don't agree see the Incompleteness Theorem. It was once thought (by Hilbert no less) that computers would one day be able to derive all mathematical truths for us. Alas, G\:{o}del came along and ruined all of those grand plans by proving such an endeavor was in possible. He also showed the limits of human reason. Computers may or may not be "dumber" than humans, but we know that they can't be "smarter."
  - ekidd 16y ago
    What kind of high-level mathematics is provably impossible for computers, but merely difficult for suitably-trained humans? If you're thinking of either of Gödel's incompleteness theorems, you may be slightly mistaken about what they say. In general, a human operating by rigorous standards of proof is no more able to prove the completeness and consistency of certain formal systems—using the tools provided by those formal systems—than a machine can. If, as a human, you somehow prove the consistency of these particular formal systems, you run smack into Gödel's second theorem: For any formal effectively generated theory T including basic arithmetical truths and also certain truths about formal provability, T includes a statement of its own consistency if and only if T is inconsistent. Thus, any proof of consistency is self-defeating, whether it's made by neurons or silicon. Really, math doesn't care what parts of the periodic table you use to prove things. :-)
perlgeek 16y ago
Actually I find that much easier than blurred text on random lines in the background
pieter 16y ago
I tried a few, and it looks like most (all?) of them can be answered by wolfram alpha.
- kahawe 16y ago
  ...which sort of defies the reason the CAPTC_H_A was put there in the first place - great!
jxcole 16y ago
I could easily write a captcha breaker for this...It's much simpler to do than one with fuzzy characters.
presto8 16y ago
This looks like the derivative of a constant value, which is always going to be zero. I reloaded the page several times, and each time, no matter how complex the formula looked, it was always a constant. Still, it is cute.
drndown2007 16y ago
Am I the only one saddened by the fact that this would have been a piece of cake back in high school/college, but can't remember how to do them (integrals) anymore? :(
- artmageddon 16y ago
  The notion of "use it or lose it" is always disappointing, but honestly if you learned them once you can learn them again.
  - pbhjpbhj 16y ago
    >if you learned them once you can learn them again I doubt this personally. I didn't have any problems with the partial differential I was set. I mean on a general level that something once learnt can be relearned.
    - artmageddon 16y ago
      You may not be as sharp at it as you were when you spent hours pounding it into your head on a frequent basis, but it's surely within a person's grasp. At least as far as math goes; something like language fluency may be another story.
- weavejester 16y ago
  I did a lot of maths in college before I moved onto programming and computer science, but I also found the problem hard. I think I could probably work it out from first principles eventually, but it's surprising how much calculus and trig comes down to memorising rules.
tydok 16y ago
The required value seems to be a small integer. A bot trying zero each time, IMO, has good odds passing the captcha.
ddbbcc 16y ago
Actually, the captcha is quite easy to extract (and solve), so it will probably filter out humans, not bots :)
farout 16y ago
As a side question, why are captchas using alphanumerics? Any reason why you can say, what is 1+1? And flip the terms and answers for each captcha. Is it because a person can't solve 3+8?
- heyitsnick 16y ago
  Because a computer is very good at solving basic maths questions? All this does is simplify the captcha for machines to solve, whilst complicating it for humans (basic maths is easy for most but it's still one more logical step then 'type out the 5 letters you see'). Instead of 26 upper and lower-case characters, and often just a random string (so we can't make a best guess vs a dictionary), we now just have ten characters and maybe 2-4 mathematical operators and it must make sense (it can't be "42+-" for example).
  - farout 16y ago
    As you stated: If computer wanted to hack it - sure it is easy enough. But I was looking for a easy way to do some verification. I asked this because I was creating a reddit clone and wanted a captcha system. I detest the ones that exist right now.
    - jcl 16y ago
      The point of most captchas is to stop someone from writing a program that abuses your system. If you're not doing that, what exactly are you "verifying"?
      - farout 16y ago
        I want to make sure a person votes only once. But if they want to game the system fine as long as they are willing to submit a captcha For another website, I used to store the IP address and do checks but for a simple system that seem to be overkill. All of the websites have no user accounts. Is there another way to do this? Where you want some voting to happen but with no user accounts. And you want it to be dirt simple.
limmeau 16y ago
I got to compute a derivative. In the spirit of reCAPTCHA, wouldn't it be more appropriate if the Captcha consisted of symbolic integration?
baberuth 16y ago
i got one of the easier ones and was confused about why this would be difficult for machines to beat. http://random.irb.hr/latexrender/pictures/bba40bf17043b0ced791685dcba29dad.gif http://random.irb.hr/latexrender/pictures/bba40bf17043b0ced7...
9ec4c12949a4f3 16y ago
... at least they don't think it's secure because I used drag and drop? People who don't understand security: stop pretending you understand security. The reason captchas look stupid is so OCR can't run on them. The reason captcha's aren't math is because computers are far better at math than humans.
robinhouston 16y ago
The hardest captcha I've come across is the audio one used by Google on https://www.google.com/accounts/NewAccount https://www.google.com/accounts/NewAccount. Click the little wheelchair icon to hear it. It's so hard to decipher, it almost comes across as a cruel joke at the expense of blind people. These are much easier, in that I can actually understand them.
- derrida 16y ago
  I will say... "additional plugins required". If your blind you will miss that.
- brlewis 16y ago
  Once at MIT a blind student was showing me his screen reader. I couldn't make sense of the sounds at all, and asked if it was in some special code. He said no, it was normal language, just really fast. He had it read the current line on his terminal (this was late '80s). I could see the words it was supposedly reading, but I still couldn't map them to the brief burst of sound that came from the screen reader. So maybe if you've been blind a while, the audio captcha isn't so hard to decipher. Keep in mind they have to make it hard for speech recognition software to decipher too.
  - battlehorse 16y ago
    A few years back I attended a tech talk from T.V.Raman (of emacspeak fame) and he was making fun of us, poor non-blind users, for being so slow at deciphering the bursts of sounds from the screen reader. He, and other blind computer scientists that were present at the talk, was so used to the screen reader that could crank its speed up to impossible speeds for non-blind users (that don't exercise their hearing sense that much). The same applied to the tiny distortions in pitch and tone that he'd use as a replacement for syntax coloring. Pretty amazing.
  - tomkarlo 16y ago
    (Was it Sam H.?) When I was at MIT I had a lab partner who was blind for I think 6.002 or 6.003. I remember that one side-effect of using a screen reader was that he easily "recited" code, which I don't think most sighted programmers could do fluently. Of course, in order to understand what he was reciting, my only hope was generally to try to type it into a text editor, format it and look at it. (And it's also hard to transcribe code being read to you.)
derrida 16y ago
Why is this here? This is easy to a)break b)solve IF you a)finished high school maths(australia) b) know about pythons ocr libraries.
l0nwlf 16y ago
Stack Overflow should use a tougher version of it. Will weed out some noise.
Luyt 16y ago
After a few reloads, I got this captcha: - 2 + 1 - 0 + 0 * 0 + 3 - 3 = ?
kahawe 16y ago
I just use http://www.random.org/ http://www.random.org/ instead and do not have to go through all that hassle.
kmak 16y ago
I run "algorithmist.com" and was getting quite a bit of spam with using only recaptcha. I was looking for something mathy.. I ended up giving mathcaptcha a go first and it seems to work well to stop the spam, but I was ready to create my q/a with algorithm questions, with the benefit that if you can't answer basic algo questions, you shouldn't edit the wiki anyways!
CWuestefeld 16y ago
What answer does it want? I got "-6-7x7". Does it want proper order of operations applied, giving -6-49=-55? Or does it want it the silly way that most (I suspect) people are going to do it, left-to-right without respect to order of operations, -13x7=-91? (oops, the asterisks give italics rather than multiplication!)
danvoell 16y ago
That's funny. I wonder if that encourages people who otherwise wouldn't sign up. It obviously self selects your clientele. I might need to implement a "2 trains leave" problem for my captcha.
stcredzero 16y ago
One thing that's occurred to me -- there's obviously an asymmetry of effort in captchas. Reliable proof that someone is human is very hard. What about reliable proof that something is not human, but an automaton? Can we make this stronger, and make it reliable proof that something is a particular automaton? It seems to me, the answer is Yes. This is actually very powerful and useful for security. (Even if you can only count on the first time it's answered.)
- A1kmm 16y ago
  Requiring that people access your site over TCP/IP is a reasonably good way to weed out clients that don't involve computers at all. Bots are user agents that don't have a human operator; browsers are user agents with a human operator. Both bots and browsers involve computers. However, as browsers can automate some tasks, and bots need human interaction at least to program them in the first place, there is a blurry line between bot and browser. CAPTCHAs try to force a certain amount of human interaction. The only reliable way to prevent human interaction between sending a request to and receiving a response from an unknown user agent is to require a response so fast as to preclude human intervention.
cynoclast 16y ago
Dumbest CAPTCHA ever. It's a math problem - which computers are great at - in highly readable text; which they're pretty good at. I expect someone talented could break it in an automated fashion in a day or less. I don't know why they don't just throw up an fairly large image of a bunch of animals, then say "Click the cutest kitten" or something that's purely subjective, and relies on human recognition abilities rather than computational ones. Maybe two of those in succession in case a computer gets lucky? Using the same method recaptcha does. Show two images, one with a known heat-map of clicks showing where people think the kitten is, to test them, and another one for them to develop the map on the new picture for future tests.
- nostromo 16y ago
  Hmmm, perhaps this is the first of many in a dystopian future of human CAPTCHAs... "Please solve this equation in 200ms or less. Sorry, no humans allowed."
  - Natsu 16y ago
    Actually, that's a fascinating idea that could be put to a different purpose. Spambots try to spew spam as quickly as possible, right? I wonder how effective it would be to flag those who fill out the signup forms too quickly as likely spammers and check up on them or impose extra limitations until they had been using their account for a while without spamming?
georgecmu 16y ago
I've seen harder (limits of converging sequences, etc), but wolfram alpha made them harder for humans than for automated scripts. My captcha was to find the least zero of this polynomial: http://random.irb.hr/latexrender/pictures/c46ad0f30d7575c609d863329f5e59f7.gif http://random.irb.hr/latexrender/pictures/c46ad0f30d7575c609... and all I had to do was to OCR the formula: http://www.wolframalpha.com/input/?i=x^3+%2B+3x^2-4x+-12+%3D%3D+0 http://www.wolframalpha.com/input/?i=x^3+%2B+3x^2-4x+-12+%3D...
mathgladiator 16y ago
No This can be automated with https://github.com/mathgladiator/tutor https://github.com/mathgladiator/tutor I'd have to spend some time working on adding OCR support, but overall totally doable,
dnsworks 16y ago
I will never sign up for any website who puts something so jerky into their website. Adding transactional friction only drives users away.
37prime 16y ago
The irony is that it would be easier to solve the captcha using programs like Mathematica.
tluyben2 16y ago
Hmm. I see captcha's harder than that every day on numerous sites; with a lot of 'normal' captcha's you sit staring for minutes and then kind of gamble (like an OCR bot) to what it says. At least the formulas are clearly readable and there is a one correct answer to each of them, while this http://bit.ly/gKPgKH http://bit.ly/gKPgKH I cannot read (Google).
- elai 16y ago
  chithersom
nickpinkston 16y ago
I found an exploit ;-) http://www.wolframalpha.com/examples/Calculus.html http://www.wolframalpha.com/examples/Calculus.html
- joetek 16y ago
  Nice, but if you can get it into Wolfram Alpha and back, you're probably human. :)
  - Xk 16y ago
    Or you can write a simple OCR program that can send HTTP requests.
    - nickpinkston 16y ago
      OCR + LaTeX, have fun! My scanned books can't tell VV and W apart...
ranit 16y ago
Of course not the hardest. http://brad.livejournal.com/2331278.html http://brad.livejournal.com/2331278.html
- Semiapies 16y ago
  That's a blog entry linking to TFA.
bugsy 16y ago
I like that captcha because I can do it in my head which makes me feel special. Too bad there isn't a button just to check the captcha for those of us who don't want to sign up for an account.
AW3nham 16y ago
Bit pretentious, bordering childish. Also easy to crack WolframAlpha if you don't know the math
georgemcbay 16y ago
The real WTF with this captcha is that to get a new one they recommend you reload the page, which will clear out everything you just typed into the form (since you probably typed that all before getting to the captcha), which is retarded. If you try to be smart and just put in a known wrong answer in hopes that it'll keep the form data and give you a new question, you get dumped to a validation page which tells you you're wrong and then tells you to go back and reload the page, which is also retarded. You still come out ahead because when you hit the back button you should get a new captcha and the browser should have saved your form data, but man, this page belongs in the UX hall of shame regardless of how you feel about math in your captchas.
- deleted 16y ago
  [deleted]
georgieporgie 16y ago
I reloaded the page and got something like 4 * -1 - (-4) = ? A subsequent reload sent it back to a more complex formula.
presidentender 16y ago
I think most of the answers are zero, and that this is largely a joke.
Keyframe 16y ago
huh, got in on my first try... 0/0x[... 0 duh :) Most are easy, but maybe scary looking to people not inclined to math?
StefanKarpinski 16y ago
The questions it generates are all trivial with a little bit of math knowledge. Finding the roots of polynomials that are already factored. Multiplying a series of factors, the last of which is zero.
hoag 16y ago
Haha this is seriously awesome... almost makes me miss doing hours and hours of calc every day :)
mkramlich 16y ago
"Here I am, brain the size of a planet, and they have me solving captchas. If anybody needs me I'll be over in the corner rusting for the next, oh, one million years." -- Marvin the Paranoid Android (with liberties taken)
pontifier 16y ago
This brings to mind a recent article about solving the "hacker news problem". It occurs to me that requiring an entrance exam of some sort could weed out users unprepared to constructively contribute to any domain specific online forum.
- pontifier 16y ago
  Well imagine my surprise when I saw an article about an event using just this sort of weeding on page 2 of hacker news... http://news.ycombinator.com/item?id=2288469 http://news.ycombinator.com/item?id=2288469
GrandMasterBirt 16y ago
WAIT, this captcha seems like its inverse, easier for computer than human to answer.

222 points by dalys 16y ago

Hardest Captcha for a human: Maybe Hardest Captcha for a machine: Not so sure ! You can just pass the equation in Wolfram Alpha directly and you have your answer! The font is crystal clear and the equation is quite simple.

pluies_public 16y ago

I thought it had to be static, but no: the captcha actually changes at each page reload. At least it will weed out the non-mathematicians easily...

ugh 16y ago
Hardly. You can just type it into WolframAlpha, that works perfectly. (Which is quite funny because you are letting the computer solve something that’s supposed to keep computers out.) You don’t even need to learn any fancy syntax, “derivative of” works great. (High school math homework would be so much easier with WolframAlpha.)

noamsml 16y ago

Most of these are really easy. I got a partial derivative of a constant. And honestly, if you can't answer basic math questions, you probably have no use for a quantum random bit generator.

akie 16y ago
and besides, I'm not entirely sure that these are "unbreakable" whatsoever. If you really want to break this, I'd do some math-specific OCR + WolframAlpha...
- spc476 16y ago
  The image is in a clean looking font, so the OCR would probably be decent. Also, the question I got (Find the least real zero of the polynomial: p(x) = x^2 + 6x + 9) I typed, as is, into Wolfram Alpha and well, look at that, x = -3.
tallanvor 16y ago
I'm not sure I'd consider calculus to be a basic math question, except in the context of uses where you have a real need for this level of randomness.
- Jach 16y ago
  <semi-sarcastic-rant />This is what [one of many things] is wrong with the educational system! Sure it's amazing that public schools have collectively taught people basic algebra (in theory), but we should set the new bar to Calculus and just keep pushing it up every so often. (I think Bayesian stats are more difficult than straight-up calculus though I'd like to see a public familiarity with both...) Calculus has been around for a pretty long time, there's plenty of good material out there to learn it and people who understand it to teach it, there's no real reason it shouldn't be required curriculum these days.
  - jmilloy 16y ago
    I would NEVER put calculus into required curriculum. Calculus is far less important than some simple number theory, logic, and the ability to think about abstract problems creatively. The tragedy is that we push towards calculus (which is really just advanced arithmetic until you get to, say college, real analysis) at the expense of these other skills.
    - HelloBeautiful 16y ago
      IMHO you don't understand Calculus good enough yourself. It's one of the most powerful tools humankind has come with. A couple of simple ideas aplicable practically everywhere.
    - Jach 16y ago
      While agreeing with the sister-child I'll also say that yes, other math and thinking skills are also important, but there's no reason we can't have those and calculus too. Throw out some of the more useless things like PE, get rid of certain requirements like art, maybe take away a year or two of the "read books most of the class doesn't care about and write essays hurriedly read over by the prof to later be never read again" English classes. Even just removing one required semester (half a year) of PE and one required semester of English (which shouldn't be very controversial) frees up two semesters, which for a high school level accommodates Calculus just fine. I'd love to see mathematical analysis courses taught at the high school level too (especially since many grown adults are under the impression math in general is like the algebra they did in high school) but that might be getting ahead of ourselves. I also don't see why you can't teach number theory et al. throughout all the math courses. I never had a formal trigonometry course because it was taught along the way.
mrchess 16y ago
Mine had a complex multiplication problem but had 0 as a multiplier. Can't get easier than that!
wiredfool 16y ago
Yep, I saw a lot of derivatives of a constant, and multiplies by zero. There were a couple that weren't obviously 0, but I wouldn't be surprised if most of the actual answers were 0.
philh 16y ago
I got "find the least real zero of the polynomial: -7 * 4 - 7". Somehow I doubt "mu" would be accepted. (That sort of think has only shown up once over multiple refreshes though.)
- repsilat 16y ago
  Just to prove you are a human, please answer the following math challenge. -6 + 5 * 0 = ? (I guess I just got lucky?)
  - thret 16y ago
    I got d/dx(2sin(3pi)+0) el oh el, I suppose I got lucky also.
- sliverstorm 16y ago
  I got that one too, and misinterpreted it as I always do and made it stupidly complex in my head. For a minute, I thought it was asking for the least real, i.e. most imaginary, zero.

makmanalp 16y ago

Ha, by this logic, a large majority of the current world population aren't humans :)

merijnv 16y ago
Well, to be fair the easiest captcha's are easy high school level equations and (as someone else already pointed out) if you can't solve these you have no business obtaining an account for extremely high quality quantum random numbers. (I believe they provide about 7.8 or 7.9 bits of entropy per byte)
- nettdata 16y ago
  I'll stick with Lavarand, thanks... good enough for my needs. http://en.wikipedia.org/wiki/Lavarand http://en.wikipedia.org/wiki/Lavarand
- pavel_lishin 16y ago
  I buy my random numbers from a guy in the alley behind my building. He says they fell off a truck.
- HelloBeautiful 16y ago
  OMG! "extremely high quality quantum random numbers" Thats an interesting product to sell.
nickolai 16y ago
It's just a little more targeted than the average captcha. It should weed out both bots and people you wouldn't want using the website in the first place.
- dhimes 16y ago
  Unless they become popular and the answers are too easy. Then you can guess the answer without even understanding the problem.
crocowhile 16y ago

shasta 16y ago

Sounds like a great way to stock up on fake accounts submitted by people who just want to know if they got the question right

knowtheory 16y ago
i even made a typo in my login handle >_< got the question right though.

loudmax 16y ago

It's a reverse captcha! If you answer too quickly it knows you're a computer.

TorbjornLunde 16y ago

Isn't using math questions to stop bots(computers), a bit like trying to stop tanks with barbed wire?

mvalle 16y ago

I don't think it would be hard to do, in fact, they reverse the whole point of a CAPTCHA. A CAPTCHA is supposed to be a task that is easy for humans, but difficult for computers. High-level mathematics is difficult for humans but easy for computers. They do have some success of telling computers and humans apart, though.

mrspeaker 16y ago
Precisely the reason I wrote the very useful "human.txt" captcha: http://www.mrspeaker.net/2010/07/15/humans-txt/ http://www.mrspeaker.net/2010/07/15/humans-txt/ Stops those pesky humans wasting precious robot bandwidth and is quite a bit harder than the Quantum Random Bit Generator captcha ;)
- deleted 16y ago
  [deleted]
iy56 16y ago
High-level mathematics is difficult for humans and provably impossible for computers.
- timtadh 16y ago
  Correct. For those that don't agree see the Incompleteness Theorem. It was once thought (by Hilbert no less) that computers would one day be able to derive all mathematical truths for us. Alas, G\:{o}del came along and ruined all of those grand plans by proving such an endeavor was in possible. He also showed the limits of human reason. Computers may or may not be "dumber" than humans, but we know that they can't be "smarter."
- ekidd 16y ago
  What kind of high-level mathematics is provably impossible for computers, but merely difficult for suitably-trained humans? If you're thinking of either of Gödel's incompleteness theorems, you may be slightly mistaken about what they say. In general, a human operating by rigorous standards of proof is no more able to prove the completeness and consistency of certain formal systems—using the tools provided by those formal systems—than a machine can. If, as a human, you somehow prove the consistency of these particular formal systems, you run smack into Gödel's second theorem: For any formal effectively generated theory T including basic arithmetical truths and also certain truths about formal provability, T includes a statement of its own consistency if and only if T is inconsistent. Thus, any proof of consistency is self-defeating, whether it's made by neurons or silicon. Really, math doesn't care what parts of the periodic table you use to prove things. :-)

perlgeek 16y ago

Actually I find that much easier than blurred text on random lines in the background

pieter 16y ago

I tried a few, and it looks like most (all?) of them can be answered by wolfram alpha.

kahawe 16y ago
...which sort of defies the reason the CAPTC_H_A was put there in the first place - great!

jxcole 16y ago

I could easily write a captcha breaker for this...It's much simpler to do than one with fuzzy characters.

presto8 16y ago

This looks like the derivative of a constant value, which is always going to be zero. I reloaded the page several times, and each time, no matter how complex the formula looked, it was always a constant. Still, it is cute.

drndown2007 16y ago

Am I the only one saddened by the fact that this would have been a piece of cake back in high school/college, but can't remember how to do them (integrals) anymore? :(

artmageddon 16y ago
The notion of "use it or lose it" is always disappointing, but honestly if you learned them once you can learn them again.
- pbhjpbhj 16y ago
  >if you learned them once you can learn them again I doubt this personally. I didn't have any problems with the partial differential I was set. I mean on a general level that something once learnt can be relearned.
  - artmageddon 16y ago
    You may not be as sharp at it as you were when you spent hours pounding it into your head on a frequent basis, but it's surely within a person's grasp. At least as far as math goes; something like language fluency may be another story.
weavejester 16y ago
I did a lot of maths in college before I moved onto programming and computer science, but I also found the problem hard. I think I could probably work it out from first principles eventually, but it's surprising how much calculus and trig comes down to memorising rules.

tydok 16y ago

The required value seems to be a small integer. A bot trying zero each time, IMO, has good odds passing the captcha.

ddbbcc 16y ago

Actually, the captcha is quite easy to extract (and solve), so it will probably filter out humans, not bots :)

farout 16y ago

As a side question, why are captchas using alphanumerics? Any reason why you can say, what is 1+1? And flip the terms and answers for each captcha. Is it because a person can't solve 3+8?

heyitsnick 16y ago
Because a computer is very good at solving basic maths questions? All this does is simplify the captcha for machines to solve, whilst complicating it for humans (basic maths is easy for most but it's still one more logical step then 'type out the 5 letters you see'). Instead of 26 upper and lower-case characters, and often just a random string (so we can't make a best guess vs a dictionary), we now just have ten characters and maybe 2-4 mathematical operators and it must make sense (it can't be "42+-" for example).
- farout 16y ago
  As you stated: If computer wanted to hack it - sure it is easy enough. But I was looking for a easy way to do some verification. I asked this because I was creating a reddit clone and wanted a captcha system. I detest the ones that exist right now.
  - jcl 16y ago
    The point of most captchas is to stop someone from writing a program that abuses your system. If you're not doing that, what exactly are you "verifying"?
    - farout 16y ago
      I want to make sure a person votes only once. But if they want to game the system fine as long as they are willing to submit a captcha For another website, I used to store the IP address and do checks but for a simple system that seem to be overkill. All of the websites have no user accounts. Is there another way to do this? Where you want some voting to happen but with no user accounts. And you want it to be dirt simple.

limmeau 16y ago

I got to compute a derivative. In the spirit of reCAPTCHA, wouldn't it be more appropriate if the Captcha consisted of symbolic integration?

baberuth 16y ago

i got one of the easier ones and was confused about why this would be difficult for machines to beat. http://random.irb.hr/latexrender/pictures/bba40bf17043b0ced791685dcba29dad.gif http://random.irb.hr/latexrender/pictures/bba40bf17043b0ced7...

9ec4c12949a4f3 16y ago

... at least they don't think it's secure because I used drag and drop? People who don't understand security: stop pretending you understand security. The reason captchas look stupid is so OCR can't run on them. The reason captcha's aren't math is because computers are far better at math than humans.

robinhouston 16y ago

The hardest captcha I've come across is the audio one used by Google on https://www.google.com/accounts/NewAccount https://www.google.com/accounts/NewAccount. Click the little wheelchair icon to hear it. It's so hard to decipher, it almost comes across as a cruel joke at the expense of blind people. These are much easier, in that I can actually understand them.

derrida 16y ago
I will say... "additional plugins required". If your blind you will miss that.
brlewis 16y ago
Once at MIT a blind student was showing me his screen reader. I couldn't make sense of the sounds at all, and asked if it was in some special code. He said no, it was normal language, just really fast. He had it read the current line on his terminal (this was late '80s). I could see the words it was supposedly reading, but I still couldn't map them to the brief burst of sound that came from the screen reader. So maybe if you've been blind a while, the audio captcha isn't so hard to decipher. Keep in mind they have to make it hard for speech recognition software to decipher too.
- battlehorse 16y ago
  A few years back I attended a tech talk from T.V.Raman (of emacspeak fame) and he was making fun of us, poor non-blind users, for being so slow at deciphering the bursts of sounds from the screen reader. He, and other blind computer scientists that were present at the talk, was so used to the screen reader that could crank its speed up to impossible speeds for non-blind users (that don't exercise their hearing sense that much). The same applied to the tiny distortions in pitch and tone that he'd use as a replacement for syntax coloring. Pretty amazing.
- tomkarlo 16y ago
  (Was it Sam H.?) When I was at MIT I had a lab partner who was blind for I think 6.002 or 6.003. I remember that one side-effect of using a screen reader was that he easily "recited" code, which I don't think most sighted programmers could do fluently. Of course, in order to understand what he was reciting, my only hope was generally to try to type it into a text editor, format it and look at it. (And it's also hard to transcribe code being read to you.)

derrida 16y ago

Why is this here? This is easy to a)break b)solve IF you a)finished high school maths(australia) b) know about pythons ocr libraries.

l0nwlf 16y ago

Stack Overflow should use a tougher version of it. Will weed out some noise.

Luyt 16y ago

After a few reloads, I got this captcha: - 2 + 1 - 0 + 0 * 0 + 3 - 3 = ?

kahawe 16y ago

I just use http://www.random.org/ http://www.random.org/ instead and do not have to go through all that hassle.

kmak 16y ago

I run "algorithmist.com" and was getting quite a bit of spam with using only recaptcha. I was looking for something mathy.. I ended up giving mathcaptcha a go first and it seems to work well to stop the spam, but I was ready to create my q/a with algorithm questions, with the benefit that if you can't answer basic algo questions, you shouldn't edit the wiki anyways!

CWuestefeld 16y ago

What answer does it want? I got "-6-7x7". Does it want proper order of operations applied, giving -6-49=-55? Or does it want it the silly way that most (I suspect) people are going to do it, left-to-right without respect to order of operations, -13x7=-91? (oops, the asterisks give italics rather than multiplication!)

danvoell 16y ago

That's funny. I wonder if that encourages people who otherwise wouldn't sign up. It obviously self selects your clientele. I might need to implement a "2 trains leave" problem for my captcha.

stcredzero 16y ago

One thing that's occurred to me -- there's obviously an asymmetry of effort in captchas. Reliable proof that someone is human is very hard. What about reliable proof that something is not human, but an automaton? Can we make this stronger, and make it reliable proof that something is a particular automaton? It seems to me, the answer is Yes. This is actually very powerful and useful for security. (Even if you can only count on the first time it's answered.)

A1kmm 16y ago
Requiring that people access your site over TCP/IP is a reasonably good way to weed out clients that don't involve computers at all. Bots are user agents that don't have a human operator; browsers are user agents with a human operator. Both bots and browsers involve computers. However, as browsers can automate some tasks, and bots need human interaction at least to program them in the first place, there is a blurry line between bot and browser. CAPTCHAs try to force a certain amount of human interaction. The only reliable way to prevent human interaction between sending a request to and receiving a response from an unknown user agent is to require a response so fast as to preclude human intervention.

cynoclast 16y ago

Dumbest CAPTCHA ever. It's a math problem - which computers are great at - in highly readable text; which they're pretty good at. I expect someone talented could break it in an automated fashion in a day or less. I don't know why they don't just throw up an fairly large image of a bunch of animals, then say "Click the cutest kitten" or something that's purely subjective, and relies on human recognition abilities rather than computational ones. Maybe two of those in succession in case a computer gets lucky? Using the same method recaptcha does. Show two images, one with a known heat-map of clicks showing where people think the kitten is, to test them, and another one for them to develop the map on the new picture for future tests.

nostromo 16y ago
Hmmm, perhaps this is the first of many in a dystopian future of human CAPTCHAs... "Please solve this equation in 200ms or less. Sorry, no humans allowed."
- Natsu 16y ago
  Actually, that's a fascinating idea that could be put to a different purpose. Spambots try to spew spam as quickly as possible, right? I wonder how effective it would be to flag those who fill out the signup forms too quickly as likely spammers and check up on them or impose extra limitations until they had been using their account for a while without spamming?

georgecmu 16y ago

I've seen harder (limits of converging sequences, etc), but wolfram alpha made them harder for humans than for automated scripts. My captcha was to find the least zero of this polynomial: http://random.irb.hr/latexrender/pictures/c46ad0f30d7575c609d863329f5e59f7.gif http://random.irb.hr/latexrender/pictures/c46ad0f30d7575c609... and all I had to do was to OCR the formula: http://www.wolframalpha.com/input/?i=x^3+%2B+3x^2-4x+-12+%3D%3D+0 http://www.wolframalpha.com/input/?i=x^3+%2B+3x^2-4x+-12+%3D...

mathgladiator 16y ago

No This can be automated with https://github.com/mathgladiator/tutor https://github.com/mathgladiator/tutor I'd have to spend some time working on adding OCR support, but overall totally doable,

dnsworks 16y ago

I will never sign up for any website who puts something so jerky into their website. Adding transactional friction only drives users away.

37prime 16y ago

The irony is that it would be easier to solve the captcha using programs like Mathematica.

tluyben2 16y ago

Hmm. I see captcha's harder than that every day on numerous sites; with a lot of 'normal' captcha's you sit staring for minutes and then kind of gamble (like an OCR bot) to what it says. At least the formulas are clearly readable and there is a one correct answer to each of them, while this http://bit.ly/gKPgKH http://bit.ly/gKPgKH I cannot read (Google).

elai 16y ago
chithersom

nickpinkston 16y ago

I found an exploit ;-) http://www.wolframalpha.com/examples/Calculus.html http://www.wolframalpha.com/examples/Calculus.html

joetek 16y ago
Nice, but if you can get it into Wolfram Alpha and back, you're probably human. :)
- Xk 16y ago
  Or you can write a simple OCR program that can send HTTP requests.
  - nickpinkston 16y ago
    OCR + LaTeX, have fun! My scanned books can't tell VV and W apart...

ranit 16y ago

Of course not the hardest. http://brad.livejournal.com/2331278.html http://brad.livejournal.com/2331278.html

Semiapies 16y ago
That's a blog entry linking to TFA.

bugsy 16y ago

I like that captcha because I can do it in my head which makes me feel special. Too bad there isn't a button just to check the captcha for those of us who don't want to sign up for an account.

AW3nham 16y ago

Bit pretentious, bordering childish. Also easy to crack WolframAlpha if you don't know the math

georgemcbay 16y ago

The real WTF with this captcha is that to get a new one they recommend you reload the page, which will clear out everything you just typed into the form (since you probably typed that all before getting to the captcha), which is retarded. If you try to be smart and just put in a known wrong answer in hopes that it'll keep the form data and give you a new question, you get dumped to a validation page which tells you you're wrong and then tells you to go back and reload the page, which is also retarded. You still come out ahead because when you hit the back button you should get a new captcha and the browser should have saved your form data, but man, this page belongs in the UX hall of shame regardless of how you feel about math in your captchas.

deleted 16y ago
[deleted]

georgieporgie 16y ago

I reloaded the page and got something like 4 * -1 - (-4) = ? A subsequent reload sent it back to a more complex formula.

presidentender 16y ago

I think most of the answers are zero, and that this is largely a joke.

Keyframe 16y ago

huh, got in on my first try... 0/0x[... 0 duh :) Most are easy, but maybe scary looking to people not inclined to math?

StefanKarpinski 16y ago

The questions it generates are all trivial with a little bit of math knowledge. Finding the roots of polynomials that are already factored. Multiplying a series of factors, the last of which is zero.

hoag 16y ago

Haha this is seriously awesome... almost makes me miss doing hours and hours of calc every day :)

mkramlich 16y ago

"Here I am, brain the size of a planet, and they have me solving captchas. If anybody needs me I'll be over in the corner rusting for the next, oh, one million years." -- Marvin the Paranoid Android (with liberties taken)

pontifier 16y ago

This brings to mind a recent article about solving the "hacker news problem". It occurs to me that requiring an entrance exam of some sort could weed out users unprepared to constructively contribute to any domain specific online forum.

pontifier 16y ago
Well imagine my surprise when I saw an article about an event using just this sort of weeding on page 2 of hacker news... http://news.ycombinator.com/item?id=2288469 http://news.ycombinator.com/item?id=2288469

GrandMasterBirt 16y ago

WAIT, this captcha seems like its inverse, easier for computer than human to answer.