I spent the evening googling...
The iButton I have for Konami is model 1991 (as mentioned above). It is protected by 3 passwords. It is vulnerable to dictionary attack..
Here is a link with a bit more information and a link to the security bulletin,
http://www.grandideastudio.com/ds1991-ibutton-dictionary-attack/There is also an executable to launch the attack. (source code included, but you need some libraries to compile it.. Use it to write your own dictionary attacker)
There are dictionaries available on the web..
However, very tired now and not sure what the reader hardware is. Math says it will take many years to crack it, but with the use of many computers it can be reduced. Also, assuming the passwords do not use extended characters the time is also reduced. Once one key is cracked we assume they use the same passwords for all keys.
Typical dictionary brute force stuff.
Interesting read, the code is very old. A reader can be made pretty simply from my googling. 1Wire interface, a USB to Serial adapter, a 1Wire IC ( DS2480B+ ) might be a good start.
What to do once the password has been discovered? Not sure. Maybe it will be clear after some rest. Maybe it is clear for someone else.
Hope someone picks up the ball and runs with it.
Attached is the source code from the zip file available from the articles in this message (made to .txt, system will not allow a .c file attachent...
Perhaps a bus sniffer between machine and iButton would reveal something good?