There is such utility for Linux systems called shred. It writes files with random values several times and then also can write it with zeroes (to hide overwriting) and delete them so that files couldn't be restored.

Is there something trustful like this for Android (preferably not proprietary, but libre software)?

  • 3
    Overwriting data in the "flash age" is next to useless as wear leveling redirects the written data to a new flash cell.
    – Robert
    Nov 15, 2020 at 16:40
  • unix.stackexchange.com/q/602498 instead of /dev/zero you can use /dev/urandom (but as Robert said it's pointless) android.stackexchange.com/q/231098
    – alecxs
    Nov 15, 2020 at 17:26
  • @Robert ok, what to do to destroy data: overwrite the whole flash memory with the other files?
    – R S
    Nov 15, 2020 at 20:18
  • 1
    made some test with the app - it is definitely related to gallery and not actually restoring deleted files. instead it finds thumbnails of previously viewed pictures. i made some screenshot and deleted from gallery. deep scan did find the screenshot. then i cleared gallery app data. second run deep scan did not find the screenshot anymore (my phone is not encrypted)
    – alecxs
    Dec 15, 2020 at 20:38
  • 1
    i can imagine the locations of thumbnails are endless. basically you need such app with option to delete results. if your device is rooted you can try to find such locations and delete files manually. if you don't ask for single files, of course a simple factory reset is sufficient
    – alecxs
    Dec 16, 2020 at 9:35


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