I recently sold a Nubia Neo 3 (Z2461) and am worried that the buyer might recover my old photos, videos, or sensitive files. Before selling it, I moved everything from the phone's internal storage to an SD card, removed the SD card, and sent some files to another device using LocalSend. I also removed my Google and other accounts, performed a factory reset, used the phone lightly afterward, and then completed several more factory resets before handing it over. Since modern Android phones generally use hardware-backed file-based encryption, does a factory reset destroy the encryption keys and make recovery tools such as DiskDigger or desktop software effectively useless? I'm mainly looking for an honest technical explanation and some reassurance.
3 Answers
Recovery apps are not magic. They may find recently deleted files on some older or unencrypted devices, but on a current Android phone using file-based encryption, a completed factory reset makes the previous internal-storage data effectively inaccessible. Doing several additional resets was unnecessary, but it does not create a practical recovery route for the old data.
Modern Android phones encrypt the internal storage, and a factory reset normally destroys the encryption keys needed to decrypt the old files. Without those keys, even someone who could extract raw storage data would generally see unusable encrypted data. Removing the SD card was also important, since files left on removable storage can have different protection depending on how the card was configured.
There is always a theoretical difference between saying something is mathematically impossible and saying it is practically recoverable. In this situation, though, recovering your old internal files would require defeating the phone’s encryption and key-management hardware, which is far beyond ordinary buyers or commercial recovery tools. The copies sent to another device are a separate consideration, so make sure that device is also secured and that the SD card remains with you.
That’s reassuring. I was mostly worried that recovery software could somehow bring everything back after the reset.