Skip to content

Instantly share code, notes, and snippets.

@Samuirai
Created June 14, 2012 20:59
Show Gist options
  • Save Samuirai/2932918 to your computer and use it in GitHub Desktop.
Save Samuirai/2932918 to your computer and use it in GitHub Desktop.
G-WAN Captcha Decode

G-WAN is a new free web server. They seem to be very proud of it, or at least just want to make a lot of money. Well anyway, in almost every sentence they write, they claim that they are 20% cooler than anything else. It feels a bit arrogant. I have to admit, I don't know a lot about web servers, so I can't speak to how good they are.

However, then I saw their Captcha example. I also don't know much about machine learning algorithms, OCR, and stuff like that, but I do know how to read pixels. I also know how to compare values with python :P

demo

They say the following about their Captcha:

[...] difficult or even completely impossible for robots.

Wait wat? If this is true, this is something really outstanding and maybe an alternative to reCaptcha...

But then I was like:

are you kidding me?

So I wrote this basic stupid pixel by pixel reading and comparing code, to decode the captcha.

smrrd$ python crack_captcha.py
GIF Image
---------
R0lGODlhGAAZAJEAAP///9//v4SkZAAAACH5BAEAAAAALAAAAAAYABkAAAJfhI+pGB0rmHuGAmtEPJj7E23VYlmbeDnMB2guu44J2lWqQi/6Drl0k7hlSKwSiHeBgV5BTK2FNOKIsmQVJekIkdzgTEOVIERY4ApDPoczTOvzCbVtq/G6kt4CK+BdRQEAOw==

Captcha Data Matrix
-------------------
                                                
  1 1 1 1               2         1 1 1 1 1     
  1       1           2 2         1             
  1       1         2   2         1             
  1       1       2     2         1 1 1 1       
  1       1       2 2 2 2 2       1             
  1       1             2         1             
  1 1 1 1               2         1             
                                                
  2 2 2 2 2         1 1 1           1 1 1       
  2               1       1       1       1     
  2                       1       1             
  2 2 2 2             1 1         1             
  2                       1       1             
  2               1       1       1       1     
  2                 1 1 1           1 1 1       
                                                
        1           2 2 2               1       
      1 1         2       2           1 1       
    1   1         2       2         1   1       
        1           2 2 2 2       1     1       
        1                 2       1 1 1 1 1     
        1         2       2             1       
        1           2 2 2               1       
                                            
color | pixel count
-------------------
    0 |        472
    1 |         81
    2 |         44

color   1 | color   2
---------------------
        3 |         4
        1 |         9
        4 |          
---------------------
        8 |        13

I also don't understand, what they think this means and why they are so excited about it:

The two sums are: 13 and 8... for the same Captcha image!
By just changing the HTML background color [...]

In the end, this was the first time I tried to solve a Captcha. I think this is the best example of how not to implement it.

YouTube Video Demo

kind regards,
samuirai

personal Website http://www.smrrd.de
I'm a member of the Stuttgart Hackerspace - shackspace

edit: to see really cool stuff with reCaptcha, check out what they did: http://www.dc949.org/projects/stiltwalker/

import base64, sys, io, Image, urllib2, re
bg = 0 # background color
cw = 8 # character width
# get the new captcha
url = urllib2.urlopen("http://62.75.175.163:8080/?captcha.c")
html = url.read().replace('\n','').replace('\r','')
url.close()
# get the base64 gif image code
# <img src="data:image/gif;base64,R0lGODlhG...AAADs=" alt="A tree" width="48" height="50" />
# => R0lGODlhG...AAADs=
regex = re.compile('.*base64,(.*)" alt')
gif_b64 = regex.match(html).group(1)
print "GIF Image"
print "---------"
print gif_b64
# load the string as image
f = io.BytesIO(base64.b64decode(gif_b64))
img = Image.open(f)
pix = img.load()
# print and analyse the pixels
print "Captcha Data Matrix"
print "-------------------"
pixels = {}
for y in xrange(0,25):
for x in xrange(0,24):
# collect data
if pix[x,y] not in pixels: pixels[pix[x,y]]=0
else: pixels[pix[x,y]]+=1
# print pixels
if pix[x,y]!=bg: print pix[x,y],
else: print ' ',
print ''
# print the analyse - total useless, but looks cool
print "color | pixel count"
print "-------------------"
for color in pixels:
print "%5d | %10d" % (color,pixels[color])
# define all characters
charset = {
0:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 1, 1, 0, 0],
[0, 1, 0, 1, 0, 1, 0, 0],
[0, 1, 1, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0]],
1:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 1, 1, 0, 0, 0],
[0, 0, 1, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0]],
2:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0, 0],
[0, 0, 1, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 0, 0]],
3:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 1, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0]],
4:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 1, 1, 0, 0, 0],
[0, 0, 1, 0, 1, 0, 0, 0],
[0, 1, 0, 0, 1, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0]],
5:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 0, 0],
[0, 1, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0]],
6:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0]],
7:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0, 0],
[0, 0, 1, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 0, 0, 0, 0]],
8:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0]],
9:
[[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 1, 0, 0],
[0, 1, 0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0, 0]],
}
def find_character(tmp_char):
highest_char = ['X',0,0,]
for char in xrange(0,10):
match = 0
fails = 0
for x in range(len(tmp_char)):
for y in range(len(tmp_char[x])):
#print str(tmp_char[x][y])+str(charset[char][x][y]),
if (charset[char][x][y] != 0 and tmp_char[x][y] != 0) or (charset[char][x][y] == tmp_char[x][y]):
match+=1
else: fails+=1
#print
#print [char,match,fails,]
if match>highest_char[1]:
highest_char=[char,match,fails,]
return highest_char
def get_color(tmp_char):
color = {}
for x in range(len(tmp_char)):
for y in range(len(tmp_char[x])):
if tmp_char[x][y]!=bg:
if tmp_char[x][y] not in color:
color[tmp_char[x][y]] = 0
else:
color[tmp_char[x][y]] += 1
return color.keys()
# analyse each character
color = {}
for yl in xrange(0,3):
for xl in xrange(0,3):
tmp_char = []
for y in xrange(yl*cw,yl*cw+cw):
tmp_line = []
for x in xrange(xl*cw,xl*cw+cw):
tmp_line.append(pix[x,y])
#print pix[x,y],
#print
tmp_char.append(tmp_line)
match = find_character(tmp_char)
col = get_color(tmp_char)
if not match[2]:
if col[0] not in color:
color[col[0]] = [match[0]]
else:
color[col[0]].append(match[0])
# print the sums
print ""
if len(color.keys())>=2:
print "color %3d | color %3d" % (color.keys()[0],color.keys()[1])
else:
print "color %3d | " % (color.keys()[0])
print "---------------------"
left_list = color[color.keys()[0]]
if len(color.keys())>=2:
right_list = color[color.keys()[1]]
else:
right_list = []
longest_length = 0
if len(left_list)>len(right_list): longest_length = len(left_list)
else: longest_length = len(right_list)
for row in xrange(0,longest_length):
left_val = ''
right_val = ''
if len(left_list)>row: left_val = str(left_list[row])
if len(right_list)>row: right_val = str(right_list[row])
print "%9s | %9s" % (left_val,right_val)
print "---------------------"
print "%9s | %9s" % (sum(left_list),sum(right_list))
@AJenbo
Copy link

AJenbo commented Oct 30, 2012

The captcha also requires that the human is able of a bit of math.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment