9 Mar
2011
9 Mar
'11
2:46 p.m.
On Tue, 08 Mar 2011 18:14:38 -0600
cctalk-request at classiccmp.org wrote:
From: Richard <legalize at xmission.com>
Subject: Re: Who will be the last HD maker down the road?
To: cctalk <cctalk at classiccmp.org>
Message-ID: <E1Px1RU-000789-Ic at shell.xmission.com>
In article <4D75366B.21696.2604652 at cclist.sydex.com>,
"Chuck Guzis" <cclist at sydex.com> writes:
I don't know how that can be true. I can understand deleting doesn't work
but is it true a simple dd if=/dev/zero of=/dev/sdx onto the flash card
doesn't fill it with zeros? And even if it doesn't, how hard is a flash
card to destroy? Hard disks are tough as nails but flash memory can be
snapped in two with your hands or a pair of pliers and burned...
We may be using flash both for external storage
and internal storage.
Flash memory is problematic for secure data. Basically, its nearly
impossible to securely erase a file from flash based disks. 
9 Mar
9 Mar
1:55 p.m.
On Wed, 9 Mar 2011, vintagecoder at aol.com wrote:
On Tue, 08 Mar 2011 18:14:38 -0600
cctalk-request at classiccmp.org wrote:
AFAIK, the "accepted" method involves a thermite grenade. :)
g
.
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From: Richard <legalize at xmission.com>
Subject: Re: Who will be the last HD maker down the road?
To: cctalk <cctalk at classiccmp.org>
Message-ID: <E1Px1RU-000789-Ic at shell.xmission.com>
In article <4D75366B.21696.2604652 at cclist.sydex.com>,
"Chuck Guzis" <cclist at sydex.com> writes:
I don't know how that can be true. I can understand deleting doesn't work
but is it true a simple dd if=/dev/zero of=/dev/sdx onto the flash card
doesn't fill it with zeros? And even if it doesn't, how hard is a flash
card to destroy? Hard disks are tough as nails but flash memory can be
snapped in two with your hands or a pair of pliers and burned...
We may be using flash both for external storage
and internal storage.
Flash memory is problematic for secure data. Basically, its nearly
impossible to securely erase a file from flash based disks. 
3:05 p.m.
On Wed, Mar 9, 2011 at 14:46, <vintagecoder at aol.com> wrote:
Writing a '0' to a location of the flash that used to be '1' MIGHT
leave the internal analogue state at a higher level than if the bit
previously was '0'. If you then operate the flash in abnormal
conditions (messing with the supply voltages) you MAY be able to get
the memory into a state where the reading thresholds are "just right"
to get the old state.
Of course, chances that anyone will actually try to steal your data
that way are close enough to 0 that if you are the kind of person to
be paranoid about those things you'd use easier ways to introduce
large amounts of entropy to the chip.
Going back on-topic (is data recoverable?) I'd say the bit-error rate
of the above method is probably way too high to rely on this as a
backup strategy.
Joe.
--
Joachim Thiemann :: http://www.tsp.ece.mcgill.ca/~jthiem
Flash memory
is problematic for secure data. ?Basically, its nearly
impossible to securely erase a file from flash based disks.
I don't know how that can be true. I can understand deleting doesn't work
but is it true a simple dd if=/dev/zero of=/dev/sdx onto the flash card
doesn't fill it with zeros? And even if it doesn't, how hard is a flash
card to destroy? Hard disks are tough as nails but flash memory can be
snapped in two with your hands or a pair of pliers and burned... 
3:06 p.m.
On 3/9/11 11:46 AM, vintagecoder at aol.com wrote:
I don't know how that can be true. I can
understand deleting doesn't work
but is it true a simple dd if=/dev/zero of=/dev/sdx onto the flash card
doesn't fill it with zeros?
From reading the papers, there are many redundant cells, and the controller
between you and the flash is free to remap and lie about what it has really
done, including continuing to erase cells that have been marked for garbage
collection long after writing has stopped. This invalidates assumptions of
repeatability of data recovery assumed for forensic evidence.
Concern from the data security folks is what is really still there
on the parts if you go directly to the chips and bypass the controller.
I'm concerned about the optimizations they mention in the controller firmware
geared to proprietary file systems (NTFS). What if these are accidentally performed
on some file system that ISN'T and NTFS file structure?
3:41 p.m.
In article <201103091946.p29Jkhmo021388 at imr-da06.mx.aol.com>,
<vintagecoder at aol.com> writes:
On Tue, 08 Mar 2011 18:14:38 -0600
cctalk-request at classiccmp.org wrote:
You can't use dd to erase an individual file.
In addition, there are all the machinations that Al mentioned. The device
pretends to be a disk, but it isn't a disk.
Read recent issues of comp.risks on usenet for more discussion on this.
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From: Richard <legalize at xmission.com>
Subject: Re: Who will be the last HD maker down the road?
To: cctalk <cctalk at classiccmp.org>
Message-ID: <E1Px1RU-000789-Ic at shell.xmission.com>
In article <4D75366B.21696.2604652 at cclist.sydex.com>,
"Chuck Guzis" <cclist at sydex.com> writes:
I don't know how that can be true. I can understand deleting doesn't work
but is it true a simple dd if=/dev/zero of=/dev/sdx onto the flash card
doesn't fill it with zeros? We may be using flash both for external storage
and internal storage.
Flash memory is problematic for secure data. Basically, its nearly
impossible to securely erase a file from flash based disks. 
3:46 p.m.
Richard wrote:
Flash memory is problematic for secure data.
Basically, its nearly
impossible to securely erase a file from flash based disks.
vintagecoder at aol.com wrote:
I don't know how that can be true. I can
understand deleting doesn't work
but is it true a simple dd if=/dev/zero of=/dev/sdx onto the flash card
doesn't fill it with zeros?
That's *exactly* the problem. It doesn't. dd only fills the blocks
that are currently in use, but the card may have spared out marginal
blocks that still contain residual user data. After that happens, there
is no normal command to the device that provides access to those blocks,
though there may be vendor-unique ways to get at them, and a well-funded
adversary almost certainly could recover that data.
This is true of modern hard drives as well.
That's why the "secure erase" commands were added to the ATA command
set, and the drive is supposed to erase even the spared blocks.
Eric
4:39 p.m.
On Mar 9, 2011, at 12:46 PM, Eric Smith wrote:
That's why the "secure erase" commands
were added to the ATA command set, and the drive is supposed to erase even the spared
blocks.
Sandforce takes this one step further in that their SSD drives have AES encryption turned
on by default. If you issue a ATA secure delete to the drive the key is wiped and
regenerated, rendering all of the data in flash, both primary and spare, into garbage.
--
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11 Mar
11 Mar
7:36 p.m.
On Wed, Mar 09, 2011 at 01:39:02PM -0800, Christian Kennedy wrote:
On Mar 9, 2011, at 12:46 PM, Eric Smith wrote:
Sounds all nice and peachy ... but I'd rather trust a disk encryption
system that can is open and can be properly verified, like the Linux
dmcrypt layer.
Kind regards,
Alex.
--
"Opportunity is missed by most people because it is dressed in overalls and
looks like work." -- Thomas A. Edison
That's why the "secure erase"
commands were added to the ATA command set, and the drive is supposed to erase even the
spared blocks.
Sandforce takes this one step further in that their SSD drives have AES
encryption turned on by default. If you issue a ATA secure delete to
the drive the key is wiped and regenerated, rendering all of the data
in flash, both primary and spare, into garbage.
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days inactive
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7 comments
8 participants
participants (8)
-
aek＠bitsavers.org -
als＠thangorodrim.de -
chris＠mainecoon.com -
eric＠brouhaha.com -
geneb＠deltasoft.com -
joachim.thiemann＠gmail.com -
legalize＠xmission.com -
vintagecoder＠aol.com