Do you want to give your Android smartphone or tablet, but be afraid of your files being exposed? Below we will see how you will make sure that all your data has been deleted. 
Before you begin, keep a backup of all your data, because as you understand if your files are deleted, they left and there is no undo.
Στη συνέχεια, συνδέστε το φορτιστή στη συσκευή σας γιατί η διαδικασία deletionIt can take a long time.
From Settings > Security > Phone Encryption (or Tablet Encryption) to start the process. On Android 4.4 or earlier devices go from Settings > Security > Lock screens to start the process.
You should guide the process. Set a strong password. You do not have to encrypt the SD card because you can just remove it and format it. Encryption can take longer than an hour.
Immediately after Settings> Backup & Restore> Factory Data Restore, then tap Reset tablet.
Once this process has been completed, your data has been deleted.
From a technical point of view, however, it is still described as free space. But if someone tries to retrieve your data they are encrypted.
However, if you want to delete them completely, proceed to the next step.
The best way to get rid of the encrypted data is to replace it with new data.
There are two different ways you can do this.
You can simply upload large files to your device (such as video which are ideal due to size) until the tray is full. Then delete the files you added.
You can also use an application like iShredder that can digitally shred data.
That's it! Your data has disappeared for good.
