Well, last night I looked at the code a bit and didn't really get anywhere.
I'm fairly suspicious of the decryption algorithm because the programer
went through great pains to make the code difficult to trace. I would
think that if the decryption were TRUELY a 960 bit IRREVERSABLE algorithm,
there would be no need to make the code difficult to trace. Granted I was
tired, so maybe it's not as difficult as I think, but it's a pain in the
butt nonetheless. If anyone else is looking at this, I have a question:
Somebody mentioned that there is a byte in the last bank of the games that
indicates where the code to run the encryption against resides. I have
been unable to determine where that byte is. All I see is the code working
on the cart between $ff00 and $ffff, where the key lies in the bytes from
$ff80 and $fff8. So I would have to assume that the only place this
information could be is $fff8/$fff9 or $fffa/$fffb?
I've altered my approach at tackling this a bit. The first thing I want to
do is get the code to successfully decrypt a cartridge using a 6502
simulator. From there I will translate the code to C, then attempt to
reverse engineer it. I won't have any time to look at this until tomorrow
though.
While getting permission to use the monitor cart would be great, I still
think it would be fun to pursue figuring out the encryption!
Bob
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