Need To Sell Some Phones - How Do I Make Sure Data Is Unrecoverable?

[SquirrelMadness]

Got a Note 3 and a couple S7 Edges to sell. Hypothetically speaking, let us say they were loaded with pics of my hairy naked body.

What's the best way to prevent these pics from surfacing?

Also user name/passwords, private keys, account info etc...

I have already flashed stock ROMS on the phones.

Was thinking of finding a random vid, like a Teletubbies episode, then load up the phones with duplicates of it to overwrite any sensitive data.

Also how do people recover sensitive data on phones? Sometimes it's best to put yourself in the position of one of these guys to check if you can recover stuff from your own wiped phone. What software do they use? I have forensic software to recover deleted files from HDDs and SSDs... have used on MicroSDs as well but never on an actual phone's flash memory.

Thanks.

 

[Richie]

I am of the understanding that, if the storage is set to encrypted in security settings then a simple reset make the data lost as the decryption part is lost so the data cannot be decrypted.

Might be wrong though

 

[Fubsy]

The note 3 will likely require a method to fill up the storage to overwrite what was there.

S7, probably ok with a factory reset as long as encryption is enabled. Do the above as well to be sure if you want, it's not going to cause any harm.

As for actually recovering data from an encrypted phone without the credentials/codes/biometrics to unlock it, I wouldn't know where to start and pretty certain it would require some illegal (to us law abiding citizens) method to break into it and access.