How to find algorithm?

f4Gg0t_43 · Post by **f4Gg0t_43** » 08 Aug 2009, 21:04

I'm wondering if there is a program that would find an algorithm for me. For example, 920219 turns into 53Td2cZ, 920220 turns into s79dhaz. I could also write a program like this but I don't know where to start. Please help, sorry if bad description.

moudy · Post by **moudy** » 09 Aug 2009, 02:34

You can actually learn python.
Its a very easy to learn language, well documented, and you can almost do any thing with it.

leetnigga · Post by **leetnigga** » 09 Aug 2009, 04:23

moudy wrote:You can actually learn python.
Its a very easy to learn language, well documented, and you can almost do any thing with it.

But it doesn't teach you cryptanalysis.

Is the length of the input always 6 and the length of the output always 7? Are you sure that the input is the only factor involved in producing the output? Does the same input always yield the same output? Where are you getting these numbers from?

moudy · Post by **moudy** » 09 Aug 2009, 04:28

oh
I didn't put cryptanalysis in mind, I over looked this part of the question.
Other members might be of better help

f4Gg0t_43 · Post by **f4Gg0t_43** » 09 Aug 2009, 12:58

leetnigga wrote:
moudy wrote:You can actually learn python.
Its a very easy to learn language, well documented, and you can almost do any thing with it.
But it doesn't teach you cryptanalysis.

Is the length of the input always 6 and the length of the output always 7? Are you sure that the input is the only factor involved in producing the output? Does the same input always yield the same output? Where are you getting these numbers from?

Always 6, and I'm always getting 7. The same for each number.

It is a captcha image that I'm trying to break, when you view the image, the URL ends in

draw.php?captcha_id=921710&seed=1249844174

but if you take away the &seed=1249844174, or change the value of it, the outcome is the same, so I think it has nothing to do with it.

leetnigga · Post by **leetnigga** » 09 Aug 2009, 13:24

CAPTCHA cracking is very difficult. It's unlikely that with just those numbers you're going to be able to work out the algorithm.

A more feasible approach is optical character recognition, writing a script to try to read the text from the image.

Can you post a few example images in this thread with their corresponding numbers and PM me a link to the site?

I might be able to help. I'll take a shot at the numbers, and if that doesn't work I'll look at OCR.

f4Gg0t_43 · Post by **f4Gg0t_43** » 09 Aug 2009, 13:34

I was thinking about OCR too, but a lot of the background pixels match the character pixels in color so it might be difficult. Here are some examples:

leetnigga · Post by **leetnigga** » 09 Aug 2009, 13:47

Those look pretty tough indeed. Send me the link so I can look at the numbers.

f4Gg0t_43 · Post by **f4Gg0t_43** » 09 Aug 2009, 14:32

http://www.newgrounds.com/join/

Every time you refresh that join page, a new captcha is created, and the URL of it is incremented by 1. But if you try to view an image that hasn't been generated it's blank, like for example http://www.newgrounds.com/captcha/draw. ... id=1000000