and what's more .. Flash memory not being infinitely over-writable, file
systems used on those devices (JFFS2 for example) actually encourage
leaving data behind by ensuring recently unlinked logical blocks aren't
re-used anytime soon (wear-leveling).
I know the original method proposed is non-destructive, but using a test
clip it's possible to dump the contents of just about any flash device.
Furthermore, given a significantly motivated adversary (and barring all
but physical destruction of the chip die itself -- not just the package)
one could also read the contents with a microscope -- even after several
erasures(*).
(*) link : http://www.cl.cam.ac.uk/~sps32/DataRem_CHES2005.pdf
But if all you're trying to do is retrieve SMS messages, it'd be a lot
easier to just subpoena the carrier .. they keep the contents forever
(even if they say they don't .. I know for a fact they do because I
personally saw one of the major US carriers .. [ahem.. Verizon] ..
deliver boxes of sent/received text messages -- for hundreds of phones
-- going back at least a year).
Cheers,
Michael Holstein CISSP GCIA
Cleveland State University
It's also possible to recover deleted photos from almost any flash card
in almost any device (camera, mobile, etc) - it's a way general purpose
file systems work. Requirement to delete information securely is
enforced in devices certified to e.g. process US military secretes. In
this case, device must follow DoD 5220-22-M recommendations and you can
expect secure erase. In general purpose operation systems and devices,
to delete information securely (wipe it) some additional
actions/utilities are usually required.
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