[guardian-dev] Is a secure wipe possible on Android?

protektor guardian protektor.guardian at gmail.com
Thu Jan 27 13:12:49 EST 2011


Hi all,

Honestly, this is an interesting one since for my manuals as well I am
dealing with the same issue...

I am in touch with a few forensics people and the one I am closest to
claims that my manual for using eraser/perm.eraser/srm is BS since
there is no longer any need for so many overwrites...

He basically says that 1-3 overwrites are more then enough on platter
drives... Even Guttmann acknowledges the fact that the mantra of 35
pass overwrite is outdated...

When it comes to flash memory he claims that 1 overwrite is plenty and
that the only thing you have to worry about is the slow decay in
discharge of the memory...

Cheerz,
Tom a.k.a. Protektor



On Thu, Jan 27, 2011 at 6:43 PM, Adrian-Ken Rueegsegger
<rueegsegger at swiss-it.ch> wrote:
> Hi,
>
> Am 27.01.2011 06:18, wrote Nathan Freitas:
>> Please tell me why this won't work[1], is a bad idea, or why this very
>> simple app doesn't exist yet for Android devices with 'dd' on them. For
>> most people, I could see this as a way to just zero out memory from time
>> to time after they delete sensitive data. The most extreme case is a
>> full wipe and zero/random of both internal and external memory.
>
> As I understand it, the issue with current SD cards and most flash
> memory for this use case is, that they perform wear-leveling [1]
> internally. This means that writes will be spread out over the free
> blocks on the flash medium.  There is an interesting paper on secure
> deletion for NAND flash file systems [2]. This might be an option to
> explore...
>
> Just my two cents,
> Adrian
>
> [1] - http://en.wikipedia.org/wiki/Wear_leveling
> [2] - http://eoslab.ssu.ac.kr/pdf/2008-5.pdf
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