Decoding File Formats/Packages

[DBG]

Hi guys, I have a PS3 tech demo (but it may as well be PSP or PC for all that I know) where aside from the regular XMB files (gif/png/jpg/etc that are not packaged), however everything else is packed into an extension called ".rb". It doesn't matter what the content is, video, sound, etc, they are all packed with this extension so I figured it's generic like pkzip.

I am not out to do anything but learn from this project (that's why I picked something that I knew wouldn't make Sony mad if I released any info about it =). So what do you guys, the pros do first? Break open an ASM debugger? Throw crates at barrels at old NEC monitors? Just hoping for some help on a starting point for this, thanks =).

[DBG]

I mean, like how did you guys open up the theme file to be able to select each file. I am not walking on illegal grounds here, I just need a push in the right direction. I can provide a file sample if that would help.

[ralferoo]

Your best bet is to just look at a hex/ASCII dump of the file and see what patterns you see. For instance, you might see filenames, you might see blocks of unecrypted data followed by tons of encrypted or compressed data, you can look for things that look like file offsets and see if the data in that position looks different to the data around it, you can look for things that look like hashes or checksums or dates, etc...

There are many ways to figure out how to extract information from a file, but it's useful to know what it's supposed to contain, whether it's based on some existing format you have documentation for, if there's any sample code that creates or uses that file, etc...

Your best bet is to look at files you already have information about and figure them out to get a feel for how it's done. e.g. how a gzip file is structured, how an ELF file fits together, etc..

But there are no hard and fast rules - it's mostly about guesswork and intuition.