web based PHP md5 crack

[kaits]

I saw one PHP web based md5 crack system that is about 700 mb

How to do somethig like that?
Some PHP skript that can encode this md5 encoded string (string = password)
5f4dcc3b5aa765d61d8327deb882cf99

on the page you enter a string into text bod and give a lenght and click on and the skript decrypts it

is something possible? I mean web based?
if not, is there any program for windows that can do that?

[Nezzar]

Haven't seen something similar yet. Why do you need in the first place? (Hopefully, nothing illegal )

[kaits]

no, nothing illegal!

I made a script that encodes string into MD5 code, but now I will make a better version og my script and add md5 decoding into string

first you enter password
and result is 5f4dcc3b5aa765d61d8327deb882cf99

then you enter 5f4dcc3b5aa765d61d8327deb882cf99
and the script will show password

is it possible? I think it sould be?