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Lately I've been thinking to get rid of some old smartphones; among them an Android device and a Blackberry. Not selling or recycling them is the ideal solution, however, I still would like to know how can I minimize the possibility of recovering data from them after the obvious wipe-out/reformat.

So my questions are:

Would it help reformatting the OS multiple times? or is there a way to zero out the memory (not sure if it would be effective as in traditional mechanical hard disks)? and would it help if I fill over and over again their memory with random data (videos, pictures, contacts, etc)?

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Ideally you encrypted the data on the phone since day one and simply following the phone's standard wipe procedure will make the data un-recoverable. Anything with flash memory (or SSD) is difficult to guarantee a complete overwrite due to the wear-levelling done at the hardware level. Reformatting would make no difference. What kind of phones are we talking about? and are they jailbroken, or rooted? –  Rod MacPherson Jun 2 '13 at 4:34
    
Thanks for the tip. It's definitely good to know about encrypting the data from the beginning. HTC Evo stock, BB Bold. How about filling the drive up with bogus data? –  Kayla Jun 2 '13 at 4:51
    
I think that is probably the best action. If you fill the drive completely you will overwrite everything. Trying to zero one bit at a time will not work as expected as the disk layout that is presented to the OS is not the actual physical layout, the drive hardware will decide which sector really gets written to and if you don't leave it with no options (by filling every other part of the disk) you can't be sure that everything really gets overwritten. –  Rod MacPherson Jun 2 '13 at 17:22
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1 Answer

up vote 5 down vote accepted

Android

  1. Use SHREDroid.
  2. Perform a factory reset.

iPhone

As of iOS 2.0, the "Erase All Content and Settings" option will actually delete and overwrite the data on your phone, rendering them unrecoverable, or remove encryption keys on devices that supports hardware encryption.

BlackBerry

The "Security Wipe" option will delete and overwrite the data on your phone.

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In case of iPhone 3GS and later, the Erase All Contents and Settings won't overwrite anything. It will just delete the cryptographic keys used for the encrypted data, thus making it impossible to recover the data. –  void_in Jun 2 '13 at 10:46
    
Great, thanks! Any documentation about the "Security Wipe" overwriting the data? –  Kayla Jun 2 '13 at 12:51
    
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