I'm thinking of implementing some kind of differencing sfdimg format for my emulator(UniPCemu). The problem is that the application needs to know if the parent image is the correct image, as well as any changes making the child invalid. What would need to be stored is probably some kind of unique ID (needs to be cross-platform, so for PC(Windows/Linux), mobile(Android) and PSP) in the parent image to check if it's actually the disk we're based on. Also, any changes to the parent would need to be identified to invalidate the child image.

Anyone has a good way to make this verification work? The disk format is already extended(current commit) to support extended information(the exact format still needs to be createn) in new disk images(not old sfdimg files).