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As far as I understand, Android 9.0 switched from Full-Disk Encryption (FDE) to File-Based Encryption (FBE), which means that encryption is done on a file-by-file basis by default.

If Android no longer encrypts the entire internal storage (or partitions) but only individual files, shouldn't it also be possible to delete individual encrypted files, preferably from an unrooted device?

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  • Going by your comments below you might wish to edit your question to include your reason – i.e. along the lines of "I need to delete {this file}, how can I do this", which would increase chances to get the answer you're after. // Apart from that: I did not check, but FBE might also encrypt the file (and directory) names – so though you might be able to delete a specific file you'd have a hard time identifying it. Next question left is: can you access that file at all (without root)?
    – Izzy
    Jul 15 at 6:54
  • @Izzy "I did not check, but FBE might also encrypt the file (and directory) names" - Did you seriously just rephrase my question and frame it as some sort of answer?? xD
    – sarahslvmn
    Jul 15 at 6:59
  • Of course, what else? You didn't even ask your real question ;) As for the quoted part: See my comment below. I'm using FBE on my Linux machine, and file names as well as directory names are encrypted along – so all you can see is "garbage". // And now it's your turn to edit your question to fit the "narrative" you really have in mind :D People can only answer questions as they are – and yours seems to miss the part you really wanted to ask (going by your comments).
    – Izzy
    Jul 15 at 7:05
  • As you don't ask the question you want to have answered, I won't place an answer – but you can read the specs yourself (keyword: metadata encryption). As for expertise, check my profile and my publications, they should speak for themselves. Also hover your mouse over the diamond next to my username for some additional clues ;) That said, I withdraw from here as I see my help is not wanted. Hope you still find the facts you're looking for.
    – Izzy
    Jul 15 at 20:21

1 Answer 1

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Warning: I am not a security expert.

The samsung link you provided says:

Each file is independently encrypted using AES-256-XTS, with a unique File Encryption Key that is derived from a Primary Key.

Which means that a non-credential encrypted (possibly unencrypted) copy of the location of the files must be stored somewhere. Therefore, in theory, if a person had physical access to the device, then they would be able to derive each files location without the user's credentials.

That being said, why are you worried about someone deleting individual files as opposed to deleting an entire disk? If someone has the ability to selectively delete data from the phones storage, then you're already screwed.

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  • @free_coupons_for_sale_1023: Actually, I'm the one in need of a deletion after accidentally uninstalling a system app via ADB shell using pm uninstall, which modifies an app configuration file inside the secured user data partition (/data/system/users/0/package-restrictions.xml to be exact). A stock version of this config file is automatically restored on boot upon deletion, so deleting this file solves my problem.
    – sarahslvmn
    Jun 23 at 11:19
  • @free_coupons_for_sale_1023: By the way, the requirement for deletion is not by my own choice, but imposed through Android's security architecture (see source.android.com/security/verifiedboot, source.android.com/security/trusty, developer.samsung.com/teegris/overview.html) which is prone to locking out the owner from his/her own data.
    – sarahslvmn
    Jun 23 at 11:20
  • That post is not related to my question and does not provide an answer either.
    – sarahslvmn
    Jun 23 at 23:41
  • Edited as there was some confusion. Changed wording from "an unencrypted (at lease not credential encrypted)" to "a non-credential encrypted (possibly unencrypted)". This is to emphasizes that meta-data may be encrypted (the samsung link doesn't specify), but not by user credentials. This means that if the person had physical access to the phone, its theoretically possible to unencrypt the meta-data (by physically extracting the DE key), without user credentials.
    – user375908
    Jul 6 at 21:34
  • No idea how you get to the conclusion that an unencrypted copy must be stored somewhere. I'm using FBE on my Linux machine, it only stores the encrypted files. The "unencrypted copy" is rather "virtual"; think of it as a "file system driver" which shows the encrypted files through an additional layer as the corresponding unencrypted content (and file name). Next, the difference to FDE is that, with the device locked, using FDE you couldn't even access the "drive" to delete anything, while with FBE you can access the disk but not read the files (or their names).
    – Izzy
    Jul 15 at 7:00

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