Question Does encrypting an Android phone also encrypt old, deleted files?

[Mr Messenger 2]

I'm going to be selling my phone soon. The advice seems to be to encrypt it then perform a Factory Reset. But does the whole internal memory get encrypted, or just the current, visible files? If so, surely that leaves old, deleted files recoverable.

 

[velocityg4]

Android 5.0 and later supports full disk encryption.

Android 6.0 and later should have shipped from the factory with encryption enabled by default.

Note: Upon further research. While it supports full disk encryption. It only encrypts currently used data. This was done so that new devices don't take a long time to boot. As the encryption key is generated on the first boot.

In cases of devices which have been in use. It does the same thing. It just takes longer as people will have built up data. Still it will only encrypt blocks marked as used.

Therefore after enabling encryption. Fill the device up with data then delete. Because of trim I would do this a couple times. Although unless you are guarding national security secrets. I don't think anyone would go to that level of work to retrieve a few bits of uncorrupted data.

This is based off Android 5. Perhaps they have revised it in later versions.

 

[Mr Messenger 2]

Android 5.0 and later supports full disk encryption.

Android 6.0 and later should have shipped from the factory with encryption enabled by default.

Note: Upon further research. While it supports full disk encryption. It only encrypts currently used data. This was done so that new devices don't take a long time to boot. As the encryption key is generated on the first boot.

In cases of devices which have been in use. It does the same thing. It just takes longer as people will have built up data. Still it will only encrypt blocks marked as used.

Therefore after enabling encryption. Fill the device up with data then delete. Because of trim I would do this a couple times. Although unless you are guarding national security secrets. I don't think anyone would go to that level of work to retrieve a few bits of uncorrupted data.

This is based off Android 5. Perhaps they have revised it in later versions.

Yes, thanks for your reply. I've been reading up on this today and that's what I've decided to do. Several times, just to be sure. I'll be filling the memory with podcasts and music videos to 100% repeatedly, interspersed with a few Factory Resets and encryptions.

Stuff national security secrets. I just don't want anyone to see pictures of me wearing my sister's underwear.