full-disclosure - Re: Disk wiping -- An alternate approach?

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Message-ID: <2d6724811001260810x76d7cc32j715c861e5ed26c18@mail.gmail.com>
Date: Tue, 26 Jan 2010 11:10:29 -0500
From: T Biehn <tbiehn@...il.com>
To: Christian Sciberras <uuf6429@...il.com>
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: Disk wiping -- An alternate approach?

Oh yeah, another note: If you use a chaining block cipher than you
only need to wipe the first block to make the rest of your data
unrecoverable. Most FDE's actually use a pw to decrypt the actual
decryption key, that block functions much the same, if you can wipe
that then the rest of the data is unusable.
Note, anyone who has pulled your key from memory via trojan or other
means at an earlier time will be able to recover your data unless the
first block of the stream has been wiped. This might be common
practice in sneak and peek routines.

-Travis

On Tue, Jan 26, 2010 at 11:04 AM, Christian Sciberras <uuf6429@...il.com> wrote:
> I was thinking, since all this (reasonable) fuss on wiping a disk over 10
> times to ensure non-readability, how come we're yet very limited on space
> usage?
> If, for example, I overwrote a bitmap file with a text one, what stops the
> computer from recovering/storing both (without using additional space)?
> Just a couple curiosities of mine.
>
>
>
>
>
> On Tue, Jan 26, 2010 at 4:08 PM, Michael Holstein
> <michael.holstein@...ohio.edu> wrote:
>>
>> > By the way, does somebody knows about the flash memory?
>> > Is zeroing a whole usb key enough to make the data unrecoverable?
>> >
>>
>> No, wear-leveling (done at the memory controller level) will dynamically
>> re-map addresses on the actual flash chip to ensure a relatively
>> consistent number of write cycles across the entire drive.
>>
>> The only way to completely "wipe" a flash disk is with a hammer.
>>
>> Regards,
>>
>> Michael Holstein
>> Cleveland State University
>>
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