About pak file Index Information

[FengPu]

ue4.26.2

I am researching the pak files of Unreal Engine, and of course, I know that many people have already studied them and there are ready-made tools available.

I hope to know more information because I cannot find any relevant information on Google search.

I encountered a problem in the second offset area of the pak file index information area.

I don't understand what 8-byte data is? The 4-byte data following this 8-byte data corresponds to the 4-byte data following the file path in the third offset area of the pak file index information area, and should be used to point to the file path.
I repackaged the same file using "UnrealPak. exe" from ue4.26.2, and this 8-byte data still appears, but it is different.

”29 E5 C2 64 38 D1 8A A6 "This is the byte I want to know.

I have provided the pak file in the attachment, which includes the file index information area after AES decryption, the pak file, and the bookmarks I have organized myself using imhex.

Or please tell me where to find the source code for version 4.26.2 of 'UnrealPak. exe', as I am not sure if it is open source.

I hope to receive your help, thank you.

 

 

pak.zip

 

[VendorX]

It's a CRC.

[ikskoks]

32 minutes ago, VendorX said:

It's a CRC.

More specific? There are like thousands of CRC algorithms 😄 

[VendorX]

Hmm ... Go to the Epics github site, clone the appropriate version of Unreal Engine, look for IPlatformFilePak (use VS or VSC to navigate), and you will find the solution.

 

@iks: what's so funny?

Edited September 9, 2025 by VendorX