(He refers to n3DS in this quote, but just pretend that's the target console in this situation.
)
Might not need to decrypt/renecrypt data folder after all.
Any chance you can write something up for rxTools to do this? I've been wanting to manually transfer over the movable.sed file so I can restore my original friend code and friend list. This would also allow me to use my old save games and other stuff from a bricked 3DS I no longer own. Since my NNID has been moved over to my current 3DS I can just copy the data over. But the movable.sed has to be modified (this appears to involve altering the KeyY string stored in the movable.sed file). The string has to be rehashed using the AES engine on the 3DS as well as the data/dbs folder being decrypted and re-encrypted. So this sounds like something rxTools could do.
Moving over SD content might take a lot of programming to do as that might also need to be decrypted from the source system and then reencrypted for the target system. (although you already have a way of dumping title keys, and the title folder of the fat16 partition. And I think you already plan on doing SD content decryption without using xorpads. It's just a matter of also doing reencryption for that then)
But having an extractor and injector of the entire dbs folder and the data folder in the fat16 partition would be a great start and would be more then enough for me.
I'm sure I'm not the only person that could benefit from this. For example, if someone had a whole bunch of important game saves/SD content/Friend Code and friend list on their 3DS and they have decrypted backups and the 3DS breaks from bricking or physical damage, being able to manually transfer over the data would be a life saver for them. I think it's only the movable.sed file that is the roadblock right now.
EDIT: Refer to this thread regarding this particular issue. It happened to be a discussion on region swapping a 3DS and this is another situation that would be helped along if you implemented this.
http://gbatemp.net/threads/nand-trading-for-region-change.384115