Clickcha - click the biggest/smallest number for CAPTCHA

by est • 16 years ago

14 34 16 years ago

warp• 16 years ago

That doesn't look at all impressive. It seems easy to write a solver for it. Especially considering most spam bots are quite happy with relatively low rates of succeeding, they can just brute-force until they find one they can solve.

est4• 16 years ago

I think they use javascript to record the coordinate (x, y) where you clicked it

on one scenario you 'll select a 24x24 square out of a 200x100 pixel picture, the success rate is 2.8%

zebra2• 16 years ago

Bots will be happy by any success rate above 0%

timelinex3• 16 years ago

I think it's higher than that. I think we can atleast use some kinda of processing to detect where the circle/square/retangles are. So, it is more like 1/9. So in 6 tries there is a 50% chance of success.

patio112• 16 years ago

Why would I pick a pixel at random when I could pick a black pixel and have better than 10% chance of getting it right regardless of the question with less than 10 lines of code?

Groxx4• 16 years ago

Clickcha is more secure than traditional text based CAPTCHAs which can be read via OCR software.

Because... circled numbers can't be read by OCR software?

Without some visual obfuscation, I fail to see how this is an improvement against bots. Simple OCR + location of match = 100% success rate (just click the middle). Improvement for users, perhaps, especially due to its simplicity... but I don't know if that's worth it.

est4• 16 years ago

> Simple OCR + location of match = 100% success rate

Sometimes it ask you to choose the biggest square, not only biggest/smallest questions. The challenge varies all the time.

For example, I can ask you to choose the biggest triangle out of some boxes, circles and stars, and the question sentence can be displayed using a line of traditional CAPTCHA

retube2• 16 years ago

ok sure, but how many permutations of different questions are there? Once you have these, it is trivial to OCR the numbers/shapes and pick the appropriate one per the question.

Groxx4• 16 years ago

I didn't catch the other question types, and the page isn't loading for me any more so I can't fiddle with it further.

I can see where that'd help (significantly), but I don't see how a captcha-reader can't also parse the key words, and interpret the image appropriately. "size-est" and "shape" / "color" is easy to rip out, and a basic OCR to detect shapes and sizes and a number is pretty basic.

And remember that the site lists Captchas as being OCR-able, and that the question sentence must be readable - quickly - by humans, so it can only be weakly obfuscated, unlike some of the shorter Captchas. That weakens an already-claimed-as-weak system, so it's easy to assume the instructions can be read. Detecting a couple key words via a smallish dictionary seems simple at worst.

A few mistakes can be ignored, because the server must allow a few - people will make them too. After all of the above, what's the success rate on a dumb interpreter? Say, one that can't understand order of words, merely their existence.

I'm not seeking to totally shoot this down - I think it's an interesting idea, and with a large number of objects and some visual obfuscation could possibly supersede Captcha. But it's achieved by adding logical complexity; to retain ease of use, visual complexity / some other form has to be sacrificed, which makes it easier to read by machines. Or, potentially, making the image quite a bit bigger, so the images / objects used can be made significantly more complex ("click the dog" when given several images).

iDope5• 16 years ago

> circled numbers can't be read by OCR software?

It doesn't have to be circled numbers (or any other text), that is just one of the possibilities.

oscardelben3• 16 years ago

I written to the website owner offering to do a port for ruby on rails. I think this clickcha will also cause curiosity in people and increase comments.

Edit: what's wrong with this?

ars• 16 years ago

Is English your first language?

Because if not you'll have a hard time understanding what I'm saying. (And if it is you have no excuse for the bad grammar.)

Basically you come across as (you sound like) a "cheerleader". You want him to hire you, so you are praising his software. But your praise is false, and doesn't add anything to the discussion.

Telling the whole world you want to do a ruby on rails port doesn't add anything to the discussion either.

oscardelben3• 16 years ago

English is not my first language, but I understand your point. I thought it was something nice after having read this page on his website: http://clickcha.com/faqs/

Thanks for the clarification, it indirectly helps me to understand both the culture and idioms of the english language.

patio112• 16 years ago

On the plus side, this is going to cost the first motivated spammer who runs into it about $50 ~ $100 to get it broken by an Eastern European programmer who is better at OCR than probably anyone on HN.

On the minus side, it is then totally useless aside from hassling actual users.

timelinex3• 16 years ago

I think he is onto something, and just needs to think it through. I think creativity should be encouraged.

wglb• 16 years ago

On the part of clickcha or on the part of the eastern european programmer?

iDope5• 16 years ago

How does this hassle users more than regular captchas? The only additional effort it adds is a bit of thinking (too much to ask these days?). You don't have to type anything and it replaces the "Submit" button so not even any extra clicks.

mooism23• 16 years ago

It replaces the [Submit] button, so I can't tab to it and press space to submit, I have to move my hand from the keyboard to use the mouse.

Ordinary captchas exclude blind and other visually-impaired people. Audio captchas exclude deaf and hard-of-hearing people. Clickcha excludes people with muscle-control disabilities.

mooism23• 16 years ago

Whatever happened to the idea of filtering out comments that looked spammy, or that linked to spammy web pages? E-mail spam filtering has come a long way, without captchas to hide behind.

Clickcha - click the biggest/smallest number for CAPTCHA

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