I had one plus 8 pro brand new phone Android 10. I sold the phone in a week's time. I never set any password or screen lock. I understand android 10 uses file-based encryption. I just did a factory reset and sold the phone. can the buyer retrieve by data though I have not set the screen password? will the file-based encryption take care?

1 Answer 1


The file encryption on Android 10 is used no matter if you have set a lock screen password or not. The file encryption does incorporate the password but an additional secret random key is also required for accessing encrypted files.

This key is erased on factory reset, so encrypted files become impossible to decrypt.

  • Thanks for your reply . Makes sense. That means my data is completely erased. And and the buyer can never retrieve. The buyer is a local mobile shop who works on software.
    – Dave
    Dec 9, 2022 at 14:06
  • Just for clarity, the factory reset deletes all the user files, correct? (Yes, some of their bytes could remain on non-volatile storage regardless, but in this case, encrypted.) Dec 18, 2022 at 20:14
  • @RockPaperLz-MaskitorCasket AFIK the user data partition is simply reformatted and the all encryption keys are erased and new keys are generated. This mostly all user data will remain but as the encryption keys are gone it can not be recovered.
    – Robert
    Dec 19, 2022 at 16:13
  • I just heard from oneplus the phone manufacturer that encryption works only when the screen password is set. Please help
    – Dave
    Dec 19, 2022 at 18:15
  • Do the controllers for the non-volatile storage chips in most Android devices perform TRIM-like functions as with SSDs? Also, do they do anything like "Read zero after TRIM"? If so, data recovery would likely require special equipment. See superuser.com/questions/1749575/why-is-this-data-seemingly-gone Dec 19, 2022 at 22:39

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