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I have a LG G8 running Android 10. Your basic, unrooted, stock ROM phone commercial phone. It has a 64GB SD card where I place most of my data.

I want to know how I could achieve the following 2 goals simultaneously:

  1. I'd like the files on the SD card to be encrypted so that if I lose my phone, the person who finds it cannot access the data on the SD card

  2. If the phone dies on me, I'd like to be able to access the data on the SD card, simply by inserting the card in a new Android phone. Since it's encrypted, I'm fine with entering a password or decryption key that I would extract from my current phone.

Caveats:

  • My future phone will be by a different manufacturer since LG has abandoned Android manufacturing. So no suggestions specific to my current phone.
  • I don't want to set up proper backup for my SD card (eg using SyncThing or similar tools). I already know how to do backups, and it's what I'll do if there is no other choice, it's just common sense.
  • I don't want to use 3rd party commercial apps or (more tolerable) open-source/F-Droid apps, though you are free to mention them for other people who find this question. I want a solution supported by the base Android OS (eg Developer Mode), or with standard tools like adb.
  • I don't want to root my phone or change my ROM from the stock

There are other questions similar to mine (5 to 10 years old), where the answer is "you can't decrypt your encrypted SD card from your old phone". But in all those questions the OP has broken his/her old phone, or forgotten the password. That is not my case, my phone still works, and I can take action to prepare for the future.

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  • Afraid you might be asking the impossible. If you want a manufacturer/device independent encryption "in userland", to my knowledge there's nothing offered by the "stock system" (you'd at least need root to extract the keys) – so going with a 3rd-party app will be your only option. You can find some candidates in my corresponding app listing.
    – Izzy
    Commented Jul 9, 2022 at 9:51
  • So even with Developer Mode and adb, I cannot extract the encryption keys, and in the future transfer them to a new phone (again by adb) when needed? Commented Jul 9, 2022 at 9:59
  • The encryption keys are bound to the device and can not be extracted. If you use an encrypted SD-card make sure you always backup it's content.
    – Robert
    Commented Jul 9, 2022 at 11:40
  • That's unfortunate. Thanks for setting the record straight. Commented Jul 9, 2022 at 12:10

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