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Author Topic: CAPTCHAs  (Read 5471 times)
Dbyt3r
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« on: August 15, 2007, 04:12:02 AM »

Well, I know lots of you guys must've cracked, or tried to crack a CAPTCHA or two.. or more  Don't make me...

So I was wondering if you guys used neural nets to do it or not, and if you did, what did you use as input?  Nerd

Just delete this post if you think it's passing some invisible boundries Smiley.
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perkiset
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« Reply #1 on: August 15, 2007, 01:21:03 PM »

Well, no real boundaries here (except those listed in forum rules...) but, that info would certainly not be posted or discussed here because of the proprietary nature...

I'm fairly certain that anyone here, if they actually had such experience Mobster would not share it in such an open forum.

I'm gonna speculate that there's other, better suited forums for that discussion... Wink

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nop_90
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« Reply #2 on: August 15, 2007, 03:37:01 PM »

Use this to clean the captcha
http://www.intel.com/technology/computing/opencv/
(make it black and white and clean out the noise)
and then isolate the individual letters.

once you have the letters isolated into like 16x16 pixel blocks feed them into an opensource neural net suitable for OCR.

The vision library has a python binding (probably only works on linux)  ROFLMAO ROFLMAO

i never pursued this past the filtering the captcha, converting to black and white and isolating the letter blocks.
(search on .edu sites for how to do this, look for computer vision).

There are better ways to break captchas for me and too much investment of time for me Cheesy
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perkiset
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« Reply #3 on: August 15, 2007, 04:37:13 PM »

Oh well crap, I forgot about Nop...  ROFLMAO
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It is now believed, that after having lived in one compound with 3 wives and never leaving the house for 5 years, Bin Laden called the U.S. Navy Seals himself.
Dbyt3r
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« Reply #4 on: August 16, 2007, 12:18:45 AM »

 ROFLMAO LOL perkiset..

nop : I used some of my own self created algos (lol Tongue) to clear the noise and stuff, and put the characters into 30x30 blocks and then just tried to matches those with a db of characters, where match is see which has more pixels in common..

needless to say.. i can only go so far with my way Tongue.. + it gets kinda slow with sometimes up to 1 second processing.. (all in python)
thanks for the info!
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nop_90
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« Reply #5 on: August 16, 2007, 01:21:13 AM »

@Dbyt3r wow Smiley. impressive.
just using the opencv functions i filtered the captcha down.
then using edge detection i made it black & white
you should look for tutorials on the net for opencv and pattern recognition etc.

If you are breaking like a million captchas probably worth while.
or if you are making something like xrumer etc.

I did not see financial viability in breaking capthca
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JasonD
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« Reply #6 on: August 16, 2007, 02:42:37 AM »

Human neural nets work great imho
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Dbyt3r
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« Reply #7 on: August 16, 2007, 09:48:41 AM »

I use captcha cracking in my social network "promotion" apps Cheesy.

And I have to automate captcha cracking, because my age wouldnt allow me to pay indians to do it Tongue.
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xr
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« Reply #8 on: August 18, 2007, 06:43:27 PM »

depending on what you're trying to do and for which site sometimes human semi-automation is the most efficient way.  other methods i've tried are the standard ocr of the image and believe it or not voice recognition because some of the larger technically savy organizations present the vision impaired with an audio recording of the text.

by far though, semi-automation is the widest used imho - captchas are becoming more and more tricky.
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