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TommyUpload, posted Mon Apr 23, 2018 4:55 pm (34296)

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Hey, I was looking around for help on working out the structure of this format and I was directed to here.

I am attempting to translate a psp visual novel based on the series Mirai Nikki however I cannot work out the file system as it is not clearly apparent like most other games. I have decompiled the eboot however it seems to only contain japanese strings relating to miscellaneous menu items and some diary entries that may be part of the bonus menus. There is also a .ptd file in the usrdata folder that based off its size I assume is where the games content is held however other than the clearly present two pngs (which are save icons) and some sounds in the WAVE format (a sub type of RIFF) which are played when hovering over the menu there is no obvious game content.

Link for the files are below and any help would be greatly appreciated, thanks.

Files

Documentation on RIFF/WAVE format

aluigi, posted Mon Apr 23, 2018 5:40 pm (34301)

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Obfuscated TOC (information about the archived files) and unknown compression algorithm used for the YKLZ compressed files so the trick of scanning the whole archive looking for the "YKLZ" magic is useless without any way to decompress the files.

TommyUpload, posted Mon Apr 23, 2018 5:59 pm (34303)

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aluigi wrote:

Obfuscated TOC (information about the archived files) and unknown compression algorithm used for the YKLZ compressed files so the trick of scanning the whole archive looking for the "YKLZ" magic is useless without any way to decompress the files.

So is there any suggested method to try and work out what the files even are or how they are encrypted? As mentioned in the OP a few of the files are in the ptd uncompressed however I can't make head or tail of the rest of the data.

aluigi, posted Mon Apr 23, 2018 6:02 pm (34305)

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You have to wait someone who wants to reverse engineer the obfuscation (that looks trivial) and moreover the compression algorithm (probably simple too), but keep your expectations very low.

TommyUpload, posted Mon Apr 23, 2018 6:04 pm (34307)

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aluigi wrote:

You have to wait someone who wants to reverse engineer the obfuscation (that looks trivial) and moreover the compression algorithm (probably simple too), but keep your expectations very low.

I'd be happy to try my hand at doing it myself since I've done a lot of rom hacking and hex editing before if you could give me anything I should look at to learn about reversing obfuscation and maybe reversing compression algorithms since I haven't actually done something like that before.

aluigi, posted Mon Apr 23, 2018 7:05 pm (34310)

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You already have the starting point: "PETA" and "YKLZ"
The rest is up to you.

TommyUpload, posted Mon Apr 23, 2018 7:07 pm (34311)

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aluigi wrote:

You already have the starting point: "PETA" and "YKLZ"
The rest is up to you.

I think I might actually be able to manage this now, thank you.