[ANN] flatulent-0.0.1 ascii captcha for the masses

A

ara.t.howard

NAME

flatulent : CAPTCHA for FIGLET.

SYNOPSIS

the flatulent gem provides brain dead simple ascii art captcha for
ruby.

URI

http://codeforpeople.com/lib/ruby
http://rubyforge.org/projects/codeforpeople

INSTALL

gem install flatulent

EXAMPLE

def index
if params.has_key? 'flatulent'
Flatulent.validate! params
end

render :inline => <<-html
<html><body>

#{ Flatulent.form }

</body></html>
html
end

DOCS

see source in lib/*
see example rails project in ./rails

ONLINE SAMPLES

http://drawohara.tumblr.com/post/4791838


enjoy

ps.

sorry for double post - dropped subject on the last one!

-a
 
S

SonOfLilit

There's no use in the "noise" unless it's made of the same ascii
characters as the letters.

But then again, ascii art captchas are severely broken and there's
nothing simple to do about it.


Aur
 
A

ara.t.howard

There's no use in the "noise" unless it's made of the same ascii
characters as the letters.
Click to expand...

the new version uses that and blowfish encoded key
But then again, ascii art captchas are severely broken and there's
nothing simple to do about it.
Click to expand...

all captchas are broken and most are also complicated. nevertheless,
they are extremely effective. i'm curious why you think ascii art
captchas are more broken than any other?

kind regards.

-a
 
J

John Joyce

the new version uses that and blowfish encoded key


all captchas are broken and most are also complicated.
nevertheless, they are extremely effective. i'm curious why you
think ascii art captchas are more broken than any other?

kind regards.

-a
Click to expand...
Beautiful! another way to do human validation on user entries online!!!
 
S

SonOfLilit

With so little grid cells and so little possible transformations,
pattern matching is much much simpler.


Aur
 
A

ara.t.howard

With so little grid cells and so little possible transformations,
pattern matching is much much simpler.
Click to expand...

exactly which 'grid' are you referring to? there is no grid and
there are no 'word' chars in the virutal grid. have you looked at
the source? check out my response to brian.

also, i'm not so sure that that it true: a modest sized ascii
captcha has around 40960000 simple combinations. the current source
uses an encoded timestamp which must be submitted with the captcha
else it's invalid. that timestamp is only valid for a few minutes
and that means a program would have to make around 20480000 posts (on
average) to the same website within a few minutes to crack it using
brute force. this seems highly unlikely to me.

(ps. neither the timestamp not key are encode in the first release,
but the repo one has this feature)

the direction i'm heading is to have all virtual grid cells
positioned via css. which means the only real way to construct a
grid is to using a rendering engine first, and then to ocr the
clipped image. i'm very confident that

a) this can be done
b) it's even more work than traditional captcha to decode
c) it's 100 times less work for web developers


i'm truly very interested in seeing if someone can actually crack
this (i'm sure that they can) with a reasonable amount of effort.
remembering that traditional captcha can be broken with a low-medium
amount of effort yet reduces spam by around 98%.

kind regards.

-a
 
J

James Edward Gray II

i'm truly very interested in seeing if someone can actually crack
this (i'm sure that they can) with a reasonable amount of effort.
remembering that traditional captcha can be broken with a low-
medium amount of effort yet reduces spam by around 98%.
Click to expand...

I wonder how solid efforts like this old Ruby Quiz are:

http://www.rubyquiz.com/quiz48.html

James Edward Gray II
 
K

Karl von Laudermann

NAME

flatulent : CAPTCHA for FIGLET.

SYNOPSIS

the flatulent gem provides brain dead simple ascii art captcha for
ruby.
Click to expand...

I'm no expert on CAPTCHAs, so I'm in no position to opine on the
effectiveness of this particular mechanism. But I will say this:
couldn't you have chosen a better name than "flatulent"? :)
 
B

Brad Phelan

Karl said:
I'm no expert on CAPTCHAs, so I'm in no position to opine on the
effectiveness of this particular mechanism. But I will say this:
couldn't you have chosen a better name than "flatulent"? :)
Click to expand...

A name does not have to be nice or "good" just memorable. This
one certainly grabbed my attention. With regards to meaning I guess
the program ingests a word and after some digestion sprays out
a mess of stuff that only with some effort can be recognized
as the stuff that went in. I assume that the author was thinking
along those lines.


_ __r___ ____] _ _
| | | ____| | __ \ | || |
| | | |#_ | |__[ | | || |_X
|-| | __| | ___/ |__ _|
| |____ | | | | O | |
|______| |_|I |_| |_|
C
q: f

If you use firefox and save your example
page "as text" the captcha pops out quite easily
as I have extracted above.

The region of the catpcha can easily be recognized
because it uses a subset of ascii characters at
a density unlikely to be used in normal text.

Once you have the correct region of text screen
screen grab it out of your editor then open it up
in GIMP. Then apply the dilate filter to join
up all the gaps. I didn't get much further
than this but I think with the correct image
processing the characters start to pop out.

I used the online OCR tool at

http://www.star-tek.com.au/ocr_demo.html

and though it wasn't able to recognize the
characters correctly it did at least recognize
the character boundaries after my simple bit
of image processing. This means that with
a bit more work it could probably be cracked.

Perhaps with the css layout techniques
the text grab feature of firefox
will munge the result to be unusable??
 

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