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m!nus



Joined: 28 Jul 2007
Posts: 202
Location: Germany

Post Captcha Reply with quote
so those who have solved it, how did you do that?
someone i know has managed to crack captchas via an ANN, so i'm curios how you did it.
Mon Feb 23, 2009 12:51 am View user's profile Send private message
papa



Joined: 29 Oct 2008
Posts: 13
Location: Germany

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I didn't bother reading the words but only compared the pictures to each other.
Wed Feb 25, 2009 1:03 pm View user's profile Send private message
Tenebrar



Joined: 13 Jan 2008
Posts: 17

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So, the repeated word is actually twice the exact same picture? I had assumed at least the angle of the word would be different.
Wed Feb 25, 2009 1:29 pm View user's profile Send private message
gfoot



Joined: 05 Sep 2007
Posts: 269
Location: Brighton, UK

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I thought the standard way to crack arbitrary captchas on a large scale was to proxy them to porn site surfers, and get the guinea-pigs to do the work without realising it.

Of course, to do that you need (a) lots of bandwidth, (b) lots of visitors, and (c) lots of porn. Hmm.
Wed Feb 25, 2009 1:56 pm View user's profile Send private message
papa



Joined: 29 Oct 2008
Posts: 13
Location: Germany

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Of course the angle is different. Only comparing the pixels won't do it.
Wed Feb 25, 2009 1:59 pm View user's profile Send private message
m!nus



Joined: 28 Jul 2007
Posts: 202
Location: Germany

Post Reply with quote
papa wrote:
I didn't bother reading the words but only compared the pictures to each other.
how can you not read the words and still compare them...
Wed Feb 25, 2009 9:40 pm View user's profile Send private message
MerickOWA



Joined: 07 Apr 2008
Posts: 182
Location: HkRkoz al KuwaiT 2019 HaCkEr 101

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You could come up with some equation as to how different each picture is from another and find the two pictures which have the lowest difference value. But thats assuming that the two pictures "look" very much the same.

I'm going to bet that they don't, but I haven't tested this to see Wink
Thu Feb 26, 2009 6:23 pm View user's profile Send private message
arthur



Joined: 23 Jul 2010
Posts: 21

Post Reply with quote
gfoot wrote:
I thought the standard way to crack arbitrary captchas on a large scale was to proxy them to porn site surfers, and get the guinea-pigs to do the work without realising it.

Of course, to do that you need (a) lots of bandwidth, (b) lots of visitors, and (c) lots of porn. Hmm.

My teacher once talked about that...
Anyway porn site is illegal in my country. Sad
Mon Aug 16, 2010 3:43 pm View user's profile Send private message
moose



Joined: 16 Jul 2010
Posts: 67

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10.001 images? Are you serious?

How long did it take for the 32 who solved it?

If I would use my standard OCR-approach, I guess it would take about 0.5-1.0 seconds per picture:
10001/(60*60) = 2 hours 46 minutes. As I would have to train it a bit, lets say 3 hours, but I have to interact only about 15 minutes, then it'll know the font .... well ... acceptable at the weekend, if I have nothing to do and a good book to read Very Happy
Wed Jul 13, 2011 11:03 am View user's profile Send private message
megabreit



Joined: 03 Jan 2009
Posts: 141

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I did not use an OCR approach but "simply" reduced the number of possible candidates.
But, reading the solved forum, there were other approaches working far better... none of them used OCR.
Fri Jul 15, 2011 3:24 pm View user's profile Send private message
moose



Joined: 16 Jul 2010
Posts: 67

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megabreit wrote:
I did not use an OCR approach but "simply" reduced the number of possible candidates.
But, reading the solved forum, there were other approaches working far better... none of them used OCR.

Ok, I've tried something much simpler as my algorithm for rotating the images makes some strange things (Has anyone experience with imagemagick? Why is the font getting smaller each time I rotate the picture?)

As 10,001 files are given, you can make 10,001 = 100,020,001 comparisons. I have reduced them with a very simple method to 245,536. But it might be possible that my method has errors. Anyway, it's too much.
Sat Jul 16, 2011 1:55 pm View user's profile Send private message
AMindForeverVoyaging
Forum Admin


Joined: 28 May 2011
Posts: 482
Location: Germany

Post Reply with quote
moose wrote:

As 10,001 files are given, you can make 10,001 = 100,020,001 comparisons.


I don't think so, since if you have compared file M with file N already, you don't need to compare file N with file M anymore. Also you don't compare a file to itself. Example:

Compare 4 things with each other:
#1 with #2
#1 with #3
#1 with #4
#2 with #3
#2 with #4
#3 with #4
= 6 comparisons total
= sum of (1 to n) where n is 3

Thus, comparing 10,001 files with each other should need sum of (1 to n) where n is 10,000. With the fomula n*(n+1)/2, that is 50,005,000 comparisons. If I am not mistaken.
Sat Jul 16, 2011 2:16 pm View user's profile Send private message
contagious



Joined: 12 May 2009
Posts: 35
Location: Greece

Post Reply with quote
moose wrote:
megabreit wrote:
I did not use an OCR approach but "simply" reduced the number of possible candidates.
But, reading the solved forum, there were other approaches working far better... none of them used OCR.

Ok, I've tried something much simpler as my algorithm for rotating the images makes some strange things (Has anyone experience with imagemagick? Why is the font getting smaller each time I rotate the picture?)

As 10,001 files are given, you can make 10,001 = 100,020,001 comparisons. I have reduced them with a very simple method to 245,536. But it might be possible that my method has errors. Anyway, it's too much.


Its because rotation != n*90 degrees is lossy.
Tue Aug 07, 2012 2:39 pm View user's profile Send private message
argyblarg



Joined: 02 Sep 2014
Posts: 8

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If anyone is still interested in this one...I suppose OCR has come a long way in the last few years, and it is viable as (part of) the way to the solution.

If you do go this route, though, you'll need a top-tier OCR and plan on some serious training time. That font is *ugh*.
Sat Apr 18, 2015 8:45 pm View user's profile Send private message
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