Hi All,

I have a disk with personal information on it that I need
to wipe.  Is there some cleaver way of using "dd" to write
the alphabet across it?  Any better ideas?  (One pass is fine.)

Many thanks,
-T

Hello,

Todd a �crit :
> 
> I have a disk with personal information on it that I need
> to wipe.  Is there some cleaver way of using "dd" to write
> the alphabet across it?  Any better ideas?  (One pass is fine.)

Why bother to write the alphabet ? Writing zeroes is just fine.

Todd wrote:
>I have a disk with personal information on it that I need
>to wipe.  Is there some cleaver way of using "dd" to write
>the alphabet across it?
>
It's amazing how, a generation into the Internet Age,
folks still haven't discovered Google or Wikipedia.
http://google.com/search?q=dd+wipe

>Any better ideas?  (One pass is fine.)
>
http://www.computerhope.com/unix/shred.htm

Pascal Hambourg wrote:
> Hello,
> 
> Todd a écrit :
>> I have a disk with personal information on it that I need
>> to wipe.  Is there some cleaver way of using "dd" to write
>> the alphabet across it?  Any better ideas?  (One pass is fine.)
> 
> Why bother to write the alphabet ? Writing zeroes is just fine.

dd if=/dev/null of=/dev/sdwhatever...

Todd wrote:

> Hi All,
> 
> I have a disk with personal information on it that I need
> to wipe.  Is there some cleaver way of using "dd" to write
> the alphabet across it?  Any better ideas?  (One pass is fine.)
> 
> Many thanks,
> -T

Yes, use "wipe"



-- 
Tim Watts

The Natural Philosopher a �crit :
> 
> dd if=/dev/null of=/dev/sdwhatever...

Rather if=/dev/zero

Pascal Hambourg wrote:

> The Natural Philosopher a écrit :
>> 
>> dd if=/dev/null of=/dev/sdwhatever...
> 
> Rather if=/dev/zero

or /dev/urandom if non zero wiping with dd is desired...

-- 
Tim Watts

On 2011-12-28, Todd <Todd@invalid.invalid> wrote:
>
> I have a disk with personal information on it that I need
> to wipe.  

There's erase and there's eliminate.  Do some research:

http://en.wikipedia.org/wiki/Data_erasure

nb

-- 
Merry Christmas and a Happy New Year

Pascal Hambourg wrote:
> The Natural Philosopher a écrit :
>> dd if=/dev/null of=/dev/sdwhatever...
> 
> Rather if=/dev/zero
yup..

notbob wrote:
> On 2011-12-28, Todd <Todd@invalid.invalid> wrote:
>> I have a disk with personal information on it that I need
>> to wipe.  
> 
> There's erase and there's eliminate.  Do some research:
> 
> http://en.wikipedia.org/wiki/Data_erasure
> 
> nb
> 
if you are paranoid take a crusher to it.

Otherwise dd will render an data on it totally inaccessible to anyone 
without the ability to strip the drive and read it almost by hand.

On 12/28/2011 11:06 AM, Tim Watts wrote:
> Pascal Hambourg wrote:
>
>> The Natural Philosopher a écrit :
>>>
>>> dd if=/dev/null of=/dev/sdwhatever...
>>
>> Rather if=/dev/zero
>
> or /dev/urandom if non zero wiping with dd is desired...
>

  Oh, I like this one!  Thank you.  -T

On 12/28/2011 10:46 AM, JeffM wrote:
> It's amazing how, a generation into the Internet Age,
> folks still haven't discovered Google or Wikipedia.

Google is a blunt instrument.  Often very helpful.
It does not offer the personal wisdom, experience,
and advice offered in friendship by a colleague
to a specific question.

Thank you for the links.

-T

"Just Google It!" the new "RTFM"

On 12/28/2011 10:47 AM, The Natural Philosopher wrote:
> Pascal Hambourg wrote:
>> Hello,
>>
>> Todd a écrit :
>>> I have a disk with personal information on it that I need
>>> to wipe. Is there some cleaver way of using "dd" to write
>>> the alphabet across it? Any better ideas? (One pass is fine.)
>>
>> Why bother to write the alphabet ? Writing zeroes is just fine.
>
> dd if=/dev/null of=/dev/sdwhatever...

Thank you!

On 12/28/2011 10:58 AM, Pascal Hambourg wrote:
> The Natural Philosopher a �crit :
>>
>> dd if=/dev/null of=/dev/sdwhatever...
>
> Rather if=/dev/zero

Thank you!

On 12/28/2011 10:49 AM, Tim Watts wrote:
> Todd wrote:
>
>> Hi All,
>>
>> I have a disk with personal information on it that I need
>> to wipe.  Is there some cleaver way of using "dd" to write
>> the alphabet across it?  Any better ideas?  (One pass is fine.)
>>
>> Many thanks,
>> -T
>
> Yes, use "wipe"


Thank you!


# yum whatprovides wipe
....
wipe-2.2.0-1.2.el6.rf.x86_64 : Secure file deletion utility
Repo        : rpmforge

On 12/28/2011 11:09 AM, notbob wrote:
> On 2011-12-28, Todd<Todd@invalid.invalid>  wrote:
>>
>> I have a disk with personal information on it that I need
>> to wipe.
>
> There's erase and there's eliminate.  Do some research:
>
> http://en.wikipedia.org/wiki/Data_erasure
>
> nb
>

I just want to make it hard for the bad guys.  Anyone
with the capability to undo a dd urandom is going to
also have the resources (and search warrants) to get
whatever they what from me anyway.

Thank you for the link,
-T

On 28/12/11 20:42, Todd wrote:
> On 12/28/2011 11:06 AM, Tim Watts wrote:
>> Pascal Hambourg wrote:
>>
>>> The Natural Philosopher a écrit :
>>>>
>>>> dd if=/dev/null of=/dev/sdwhatever...
>>>
>>> Rather if=/dev/zero
>>
>> or /dev/urandom if non zero wiping with dd is desired...
>>
>
> Oh, I like this one! Thank you. -T

Writing from /dev/urandom is slower than from /dev/zero, and makes 
absolutely no difference to the security.

Writing zeros has a few advantages (though they are unlikely to be 
useful in practice) - if you use the disk to form a raid array along 
with other zeroed disks, the initial sync will be faster.  And if you 
ever feel the need to do a full disk image copy, the copy will be very 
compressible.

On Wed, 28 Dec 2011 14:42:36 -0500, Todd <Todd@invalid.invalid> wrote:

> On 12/28/2011 11:06 AM, Tim Watts wrote:
>> Pascal Hambourg wrote:

>>> The Natural Philosopher a écrit :
>>>> dd if=/dev/null of=/dev/sdwhatever...
>>> Rather if=/dev/zero
>> or /dev/urandom if non zero wiping with dd is desired...

>   Oh, I like this one!  Thank you.  -T

You can speed it up quite a bit.  Check the output of
"hdparm -i /dev/sdb|grep MultSect" for the drive in question.

Both of my hard drives are currently set to a MultSect of 16,
meaning the drive can write up to 16 sectors at a time.

So if I were wiping the drive, I'd use
"dd if=/dev/urandom of=/dev/sdb bs=8K".

Writing 16 sectors at a time instead of 1, will have a very
noticeable speed increase.

Regards, Dave Hodgins

-- 
Change nomail.afraid.org to ody.ca to reply by email.
(nomail.afraid.org has been set up specifically for
use in usenet. Feel free to use it yourself.)

On 28/12/11 20:22, The Natural Philosopher wrote:
> notbob wrote:
>> On 2011-12-28, Todd <Todd@invalid.invalid> wrote:
>>> I have a disk with personal information on it that I need
>>> to wipe.
>>
>> There's erase and there's eliminate. Do some research:
>>
>> http://en.wikipedia.org/wiki/Data_erasure
>>
>> nb
>>
> if you are paranoid take a crusher to it.

Good advice.

>
> Otherwise dd will render an data on it totally inaccessible to anyone
> without the ability to strip the drive and read it almost by hand.

A simple dd from /dev/zero is the fastest way to wipe a disk (other than 
losing the key to an encrypted disk), and makes everything completely 
inaccessible except perhaps for re-mapped bad blocks.  It doesn't matter 
if the "bad guys" can strip the disk and put it under an electron 
microscope - the idea of recovering overwritten data is a myth kept 
alive by people selling "secure disk wipe" software and hardware.

David W. Hodgins a �crit :
> 
> You can speed it up quite a bit.  Check the output of
> "hdparm -i /dev/sdb|grep MultSect" for the drive in question.
> 
> Both of my hard drives are currently set to a MultSect of 16,
> meaning the drive can write up to 16 sectors at a time.
> 
> So if I were wiping the drive, I'd use
> "dd if=/dev/urandom of=/dev/sdb bs=8K".
> 
> Writing 16 sectors at a time instead of 1, will have a very
> noticeable speed increase.

Yes, but this has probably nothing to do with the multiple sector
parameter of hadparm (see -m). This parameter is used only in PIO mode,
but disk transfers use mostly DMA modes, which are more efficient.

On 2011-12-28, The Natural Philosopher <tnp@invalid.invalid> wrote:
> notbob wrote:
>> On 2011-12-28, Todd <Todd@invalid.invalid> wrote:
>>> I have a disk with personal information on it that I need
>>> to wipe.  
>> 
>> There's erase and there's eliminate.  Do some research:
>> 
>> http://en.wikipedia.org/wiki/Data_erasure
>> 
>> nb
>> 
> if you are paranoid take a crusher to it.
>
> Otherwise dd will render an data on it totally inaccessible to anyone 
> without the ability to strip the drive and read it almost by hand.

And almost certainly not even then. Manufacturers spend huge amounts of
money trying to extract the absolutely maximum data density from the
drives. Any data which survives writing 0 to evey byte is clearly data
which could be harvested to increase the data density on the drive. 

unruh wrote:

> On 2011-12-28, The Natural Philosopher <tnp@invalid.invalid> wrote:
>> notbob wrote:
>>> On 2011-12-28, Todd <Todd@invalid.invalid> wrote:
>>>> I have a disk with personal information on it that I need
>>>> to wipe.
>>> 
>>> There's erase and there's eliminate.  Do some research:
>>> 
>>> http://en.wikipedia.org/wiki/Data_erasure
>>> 
>>> nb
>>> 
>> if you are paranoid take a crusher to it.
>>
>> Otherwise dd will render an data on it totally inaccessible to anyone
>> without the ability to strip the drive and read it almost by hand.
> 
> And almost certainly not even then. Manufacturers spend huge amounts of
> money trying to extract the absolutely maximum data density from the
> drives. Any data which survives writing 0 to evey byte is clearly data
> which could be harvested to increase the data density on the drive.

http://en.wikipedia.org/wiki/Data_remanence

is worth a look.

Whilst it is acknowledged that overwriting will make it fairly impossible 
for mere mortals to recover data, the USA's DoD and NSA require more 
stringent destruction methods.

-- 
Tim Watts

On 2011-12-29, Tim Watts <tw+usenet@dionic.net> wrote:
> unruh wrote:
>
>> On 2011-12-28, The Natural Philosopher <tnp@invalid.invalid> wrote:
>>> notbob wrote:
>>>> On 2011-12-28, Todd <Todd@invalid.invalid> wrote:
>>>>> I have a disk with personal information on it that I need
>>>>> to wipe.
>>>> 
>>>> There's erase and there's eliminate.  Do some research:
>>>> 
>>>> http://en.wikipedia.org/wiki/Data_erasure
>>>> 
>>>> nb
>>>> 
>>> if you are paranoid take a crusher to it.
>>>
>>> Otherwise dd will render an data on it totally inaccessible to anyone
>>> without the ability to strip the drive and read it almost by hand.
>> 
>> And almost certainly not even then. Manufacturers spend huge amounts of
>> money trying to extract the absolutely maximum data density from the
>> drives. Any data which survives writing 0 to evey byte is clearly data
>> which could be harvested to increase the data density on the drive.
>
> http://en.wikipedia.org/wiki/Data_remanence
>
> is worth a look.
>
> Whilst it is acknowledged that overwriting will make it fairly impossible 
> for mere mortals to recover data, the USA's DoD and NSA require more 
> stringent destruction methods.

That entry is very old. As I said, IF there really were that kind of
data remaining on the disk, the manufacturers could use it to store more
information on the disk. It is to their advantage to make use of every
last possible bit of information from the disk. 

If fact if you had read the Wikipedia page you would have seen the
following paragraphs.

------------------------------------------------------

"Daniel Feenberg, an economist at the private National Bureau of
Economic Research, claims that the chances of overwritten data being
recovered from a modern hard drive amount to "urban legend".[3] He also
points to the "18� minute gap" Rose Mary Woods created on a tape of
Richard Nixon discussing the Watergate break-in. Erased information in
the gap has not been recovered, and Feenberg claims doing so would be an
easy task compared to recovery of a modern high density digital signal.

As of November 2007, the United States Department of Defense considers
overwriting acceptable for clearing magnetic media within the same
security area/zone, but not as a sanitization method. Only degaussing or
physical destruction is acceptable for the latter.[4]

On the other hand, according to the 2006 NIST Special Publication 800-88
(p. 7): "Studies have shown that most of today?s media can be
effectively cleared by one overwrite" and "for ATA disk drives
manufactured after 2001 (over 15 GB) the terms clearing and purging have
converged."[1] An analysis by Wright et al. of recovery techniques,
including magnetic force microscopy, also concludes that a single wipe
is all that is required for modern drives. They point out that the long
time required for multiple wipes "has created a situation where many
organisations ignore the issue all together ? resulting in data leaks
and loss. "[5]"

--------------------------------------------------------


Hwever, disks are cheap. If you are really really worried, then erase
the disk, and then destroy it. Eg open the drive and heat the platter to
red hot to get above the Curie temperature. 



>

On 29/12/2011 07:23, Tim Watts wrote:
> unruh wrote:
>
>> On 2011-12-28, The Natural Philosopher<tnp@invalid.invalid>  wrote:
>>> notbob wrote:
>>>> On 2011-12-28, Todd<Todd@invalid.invalid>  wrote:
>>>>> I have a disk with personal information on it that I need
>>>>> to wipe.
>>>>
>>>> There's erase and there's eliminate.  Do some research:
>>>>
>>>> http://en.wikipedia.org/wiki/Data_erasure
>>>>
>>>> nb
>>>>
>>> if you are paranoid take a crusher to it.
>>>
>>> Otherwise dd will render an data on it totally inaccessible to anyone
>>> without the ability to strip the drive and read it almost by hand.
>>
>> And almost certainly not even then. Manufacturers spend huge amounts of
>> money trying to extract the absolutely maximum data density from the
>> drives. Any data which survives writing 0 to evey byte is clearly data
>> which could be harvested to increase the data density on the drive.
>
> http://en.wikipedia.org/wiki/Data_remanence
>
> is worth a look.
>
> Whilst it is acknowledged that overwriting will make it fairly impossible
> for mere mortals to recover data, the USA's DoD and NSA require more
> stringent destruction methods.
>

Just because the USA DoD and NSA require multiple write passes, does not 
mean that has any basis in reality.

If it were possible to recover wiped data, there would be commercial 
companies offering the service.  (And if you think the DoD or NSA have 
"silenced" such commercial efforts, you are seriously paranoid.)

I'm afraid I can't remember where, but I read an article about a 
university group that attempted to recover single-pass wiped data from a 
relatively modern hard disk (a few years old).  They worked on a section 
containing about 25 to 30 bits, and after months of work they were 
reasonably sure they had recovered some of them (11 bits, IIRC).  So I 
don't think you need to worry about any "bad guys" reading your wiped data.

The only way to be entirely sure that there is no data left on remapped 
blocks is to physically destroy the platters.  Shredding them works 
well.  But if you want to keep the disk, writing over once with zeros is 
fine.

Note that it's a different matter entirely with SSD's.  Writing over 
with zeros (or 0xff) will stop any amateurs, but groups that are willing 
to open the device and de-solder the chips will find lots of bits and 
pieces - far more than on harddisks re-mapped sectors, and with far less 
effort.  If you need to protect against that sort of thing, encrypt the 
disk before use, or destroy it physically.

David Brown wrote:
> On 29/12/2011 07:23, Tim Watts wrote:
>> unruh wrote:
>>
>>> On 2011-12-28, The Natural Philosopher<tnp@invalid.invalid>  wrote:
>>>> notbob wrote:
>>>>> On 2011-12-28, Todd<Todd@invalid.invalid>  wrote:
>>>>>> I have a disk with personal information on it that I need
>>>>>> to wipe.
>>>>>
>>>>> There's erase and there's eliminate.  Do some research:
>>>>>
>>>>> http://en.wikipedia.org/wiki/Data_erasure
>>>>>
>>>>> nb
>>>>>
>>>> if you are paranoid take a crusher to it.
>>>>
>>>> Otherwise dd will render an data on it totally inaccessible to anyone
>>>> without the ability to strip the drive and read it almost by hand.
>>>
>>> And almost certainly not even then. Manufacturers spend huge amounts of
>>> money trying to extract the absolutely maximum data density from the
>>> drives. Any data which survives writing 0 to evey byte is clearly data
>>> which could be harvested to increase the data density on the drive.
>>
>> http://en.wikipedia.org/wiki/Data_remanence
>>
>> is worth a look.
>>
>> Whilst it is acknowledged that overwriting will make it fairly impossible
>> for mere mortals to recover data, the USA's DoD and NSA require more
>> stringent destruction methods.
>>
> 
> Just because the USA DoD and NSA require multiple write passes, does not 
> mean that has any basis in reality.
> 
> If it were possible to recover wiped data, there would be commercial 
> companies offering the service.  (And if you think the DoD or NSA have 
> "silenced" such commercial efforts, you are seriously paranoid.)
> 
> I'm afraid I can't remember where, but I read an article about a 
> university group that attempted to recover single-pass wiped data from a 
> relatively modern hard disk (a few years old).  They worked on a section 
> containing about 25 to 30 bits, and after months of work they were 
> reasonably sure they had recovered some of them (11 bits, IIRC).  So I 
> don't think you need to worry about any "bad guys" reading your wiped data.
> 
> The only way to be entirely sure that there is no data left on remapped 
> blocks is to physically destroy the platters.  Shredding them works 
> well.  But if you want to keep the disk, writing over once with zeros is 
> fine.
> 
> Note that it's a different matter entirely with SSD's.  Writing over 
> with zeros (or 0xff) will stop any amateurs, but groups that are willing 
> to open the device and de-solder the chips will find lots of bits and 
> pieces - far more than on harddisks re-mapped sectors, and with far less 
> effort.  If you need to protect against that sort of thing, encrypt the 
> disk before use, or destroy it physically.
> 
+1.

The ability to recover erased data from actual drives is theoretical 
only. No practical or simple method exists to do it.

The big leap is between simply deleting files - which merely marks the 
sector involved as 'available for re use' but does not erase the actual 
data - and actually overwriting it.

At that point data recovery changes from 'something a spotty teenager 
can do in his bedroom' to 'something a computer laboratory and thousands 
of hours cant guarantee to get more than a fragment pack from'

In fact its probably easier to recover it off a disk that  has been crushed.

In the commercial arena, where old PCS and servers are regularly 
decommissioned to make way for new, crushing is used because its CHEAPER 
than erasure. And it feels more secure to insurance companies.

You can crush a big disk in seconds. It takes hours to erase it.

On 29/12/2011 11:28, The Natural Philosopher wrote:
> David Brown wrote:
>> On 29/12/2011 07:23, Tim Watts wrote:
>>> unruh wrote:
>>>
>>>> On 2011-12-28, The Natural Philosopher<tnp@invalid.invalid> wrote:
>>>>> notbob wrote:
>>>>>> On 2011-12-28, Todd<Todd@invalid.invalid> wrote:
>>>>>>> I have a disk with personal information on it that I need
>>>>>>> to wipe.
>>>>>>
>>>>>> There's erase and there's eliminate. Do some research:
>>>>>>
>>>>>> http://en.wikipedia.org/wiki/Data_erasure
>>>>>>
>>>>>> nb
>>>>>>
>>>>> if you are paranoid take a crusher to it.
>>>>>
>>>>> Otherwise dd will render an data on it totally inaccessible to anyone
>>>>> without the ability to strip the drive and read it almost by hand.
>>>>
>>>> And almost certainly not even then. Manufacturers spend huge amounts of
>>>> money trying to extract the absolutely maximum data density from the
>>>> drives. Any data which survives writing 0 to evey byte is clearly data
>>>> which could be harvested to increase the data density on the drive.
>>>
>>> http://en.wikipedia.org/wiki/Data_remanence
>>>
>>> is worth a look.
>>>
>>> Whilst it is acknowledged that overwriting will make it fairly
>>> impossible
>>> for mere mortals to recover data, the USA's DoD and NSA require more
>>> stringent destruction methods.
>>>
>>
>> Just because the USA DoD and NSA require multiple write passes, does
>> not mean that has any basis in reality.
>>
>> If it were possible to recover wiped data, there would be commercial
>> companies offering the service. (And if you think the DoD or NSA have
>> "silenced" such commercial efforts, you are seriously paranoid.)
>>
>> I'm afraid I can't remember where, but I read an article about a
>> university group that attempted to recover single-pass wiped data from
>> a relatively modern hard disk (a few years old). They worked on a
>> section containing about 25 to 30 bits, and after months of work they
>> were reasonably sure they had recovered some of them (11 bits, IIRC).
>> So I don't think you need to worry about any "bad guys" reading your
>> wiped data.
>>
>> The only way to be entirely sure that there is no data left on
>> remapped blocks is to physically destroy the platters. Shredding them
>> works well. But if you want to keep the disk, writing over once with
>> zeros is fine.
>>
>> Note that it's a different matter entirely with SSD's. Writing over
>> with zeros (or 0xff) will stop any amateurs, but groups that are
>> willing to open the device and de-solder the chips will find lots of
>> bits and pieces - far more than on harddisks re-mapped sectors, and
>> with far less effort. If you need to protect against that sort of
>> thing, encrypt the disk before use, or destroy it physically.
>>
> +1.
>

You are correct, except for the scale of the issue.

> The ability to recover erased data from actual drives is theoretical
> only. No practical or simple method exists to do it.
>

It was only ever theoretically possible with older disk technologies - 
with modern ones, it is not even theoretically possible.

> The big leap is between simply deleting files - which merely marks the
> sector involved as 'available for re use' but does not erase the actual
> data - and actually overwriting it.
>

Correct.

> At that point data recovery changes from 'something a spotty teenager
> can do in his bedroom' to 'something a computer laboratory and thousands
> of hours cant guarantee to get more than a fragment pack from'
>

When it comes to recovering overwritten data, it was "something a 
computer laboratory and thousands of hours can't guarantee to get more 
than a fragment from" about 15 years ago, when Peter Gutmann first wrote 
his widely misunderstood paper.  With modern hard disks, it is well 
within the range of easily proven to be impossible (by looking at the 
signal to noise ratios).

> In fact its probably easier to recover it off a disk that has been crushed.
>

That's perfectly true.  There have been occasions when disks have been 
recovered after fires, plane crashes, etc.

> In the commercial arena, where old PCS and servers are regularly
> decommissioned to make way for new, crushing is used because its CHEAPER
> than erasure. And it feels more secure to insurance companies.
>
> You can crush a big disk in seconds. It takes hours to erase it.

Very true.

On Wed, 28 Dec 2011 10:09:15 -0800, Todd wrote:

> Hi All,
> 
> I have a disk with personal information on it that I need to wipe.  Is
> there some cleaver way of using "dd" to write the alphabet across it? 
> Any better ideas?  (One pass is fine.)
> 
> Many thanks,
> -T

Run badblocks on it in destructive mode. Badblocks writes patterns over 
all of the sectors.

On 12/29/2011 06:43 AM, General Schvantzkoph wrote:
> On Wed, 28 Dec 2011 10:09:15 -0800, Todd wrote:
>
>> Hi All,
>>
>> I have a disk with personal information on it that I need to wipe.  Is
>> there some cleaver way of using "dd" to write the alphabet across it?
>> Any better ideas?  (One pass is fine.)
>>
>> Many thanks,
>> -T
>
> Run badblocks on it in destructive mode. Badblocks writes patterns over
> all of the sectors.
>

Thank you!

On 2011-12-29, David Brown <david@westcontrol.removethisbit.com> wrote:
>
> If it were possible to recover wiped data, there would be commercial 
> companies offering the service.  (And if you think the DoD or NSA have 
> "silenced" such commercial efforts, you are seriously paranoid.)

That's what I've seen argued here and there when this subject comes up
(and it comes up very often). When you point out that nobody seems to be
able to _demonstrate_ the recoverability of "wiped" data, people pop up
to say that the men in black are capable of doing so but don't want you
to know about it.

As a layman, I'd think there'd be a theoretical (scientific) possibility
perhaps, coupled with a practical impossibility.

Anyway, the OP is always just some dude with nude pics of his gf and
perhaps a stray tax form on his drive, so the whole discussion is a kind
of ridiculous and vain digression.  

Or maybe I'm wrong.  Maybe "Todd" is somebody with data so vital on his
'puter that hordes of intelligence agents will be willing to increase
the entropy of the universe to the point of stasis in order to try to
pierce his secrets.

Which is why he posts the crucial question on USENET.

On 30/12/11 17:22, Curt wrote:
> On 2011-12-29, David Brown<david@westcontrol.removethisbit.com>  wrote:
>>
>> If it were possible to recover wiped data, there would be commercial
>> companies offering the service.  (And if you think the DoD or NSA have
>> "silenced" such commercial efforts, you are seriously paranoid.)
>
> That's what I've seen argued here and there when this subject comes up
> (and it comes up very often). When you point out that nobody seems to be
> able to _demonstrate_ the recoverability of "wiped" data, people pop up
> to say that the men in black are capable of doing so but don't want you
> to know about it.
>

People always seem to think there are "men in black" who have more 
advanced technology than everyone else, and keep these things as state 
secrets.  But in western society, with USA in the lead, commercial 
forces trump state secrecy.  Whenever there is a lot of money to be 
made, you can be sure someone will be making it if at all possible - 
regardless of what the MiB's would prefer.

> As a layman, I'd think there'd be a theoretical (scientific) possibility
> perhaps, coupled with a practical impossibility.
>
> Anyway, the OP is always just some dude with nude pics of his gf and
> perhaps a stray tax form on his drive, so the whole discussion is a kind
> of ridiculous and vain digression.
>
> Or maybe I'm wrong.  Maybe "Todd" is somebody with data so vital on his
> 'puter that hordes of intelligence agents will be willing to increase
> the entropy of the universe to the point of stasis in order to try to
> pierce his secrets.
>
> Which is why he posts the crucial question on USENET.

On Wed, 28 Dec 2011 10:09:15 -0800, Todd wrote:
> I have a disk with personal information on it that I need to wipe.

I've been watching the thread with growing frustration, and I'm amazed
no-one's suggested what to me is the obvious solution... DBAN.

DBAN is a purpose-written application to do exactly what you want. See
www.dban.org for details. It's also available as part of the SysRescueCD
installation, which I find contains a really useful suite of tools,
and can run from a USB stick.

Chris

On 01/01/12 15:49, Chris Davies wrote:
> On Wed, 28 Dec 2011 10:09:15 -0800, Todd wrote:
>> I have a disk with personal information on it that I need to wipe.
>
> I've been watching the thread with growing frustration, and I'm amazed
> no-one's suggested what to me is the obvious solution... DBAN.
>
> DBAN is a purpose-written application to do exactly what you want. See
> www.dban.org for details. It's also available as part of the SysRescueCD
> installation, which I find contains a really useful suite of tools,
> and can run from a USB stick.
>
> Chris

There are plenty of programs designed to "securely wipe" disks using 
multiple passes.  They are /all/ useless.  A single pass is much faster, 
and does just as good a job.  A "ATA secure erase" command is quite 
similar in practice.  There is no recoverable data left on the disk 
after a single pass, except possibly in bad blocks.  And multi-pass 
"Gutmann" pattern utilities will also leave this bad-block loophole.

The only possible use of something like dban is for people who can't 
type "dd if=/dev/zero of=/dev/sda bs=1M".

On 01/02/2012 12:49 PM, David Brown wrote:
> bs=1M"

Thank you!

David Brown <david.brown@removethis.hesbynett.no> wrote:
> There are plenty of programs designed to "securely wipe" disks using 
> multiple passes.  They are /all/ useless.  A single pass is much faster, 
> and does just as good a job.

Opinion or fact? I'd be curious for a reference to that, please.

Cheers,
Chris

On 03/01/2012 09:56, Chris Davies wrote:
> David Brown<david.brown@removethis.hesbynett.no>  wrote:
>> There are plenty of programs designed to "securely wipe" disks using
>> multiple passes.  They are /all/ useless.  A single pass is much faster,
>> and does just as good a job.
>
> Opinion or fact? I'd be curious for a reference to that, please.
>
> Cheers,
> Chris

<http://en.wikipedia.org/wiki/Gutmann_method#Criticism>

People or websites with any sort of "official" standing are always 
reluctant to give concrete opinions in matters like this, especially 
when there are various government-backed standards (such as from the USA 
DoD, and many other countries around the world) that are based on 
misunderstandings of Gutmann's original paper.

The biggest piece of evidence for the impossibility (or at least total 
impractibility) of recovering overwritten data is the lack of evidence - 
if it could be done in real life, rather than just in conspiracy 
theories, then we would have heard of it.  Someone would be getting a 
great deal of prestige, and a great deal of money, by publishing the fact.

To me, this is fact.  But since I have no qualifications here, then to 
you it is just my opinion.  Don't rely on my opinion to hide evidence of 
your secret information!

David Brown <david@westcontrol.removethisbit.com> wrote:
> On 03/01/2012 09:56, Chris Davies wrote:
>> David Brown<david.brown@removethis.hesbynett.no>  wrote:
>>> There are plenty of programs designed to "securely wipe" disks using
>>> multiple passes.  They are /all/ useless.  A single pass is much faster,
>>> and does just as good a job.

> <http://en.wikipedia.org/wiki/Gutmann_method#Criticism>

Thanks.
Chris

On 12/28/2011 10:09 AM, Todd wrote:
> Hi All,
>
> I have a disk with personal information on it that I need
> to wipe. Is there some cleaver way of using "dd" to write
> the alphabet across it? Any better ideas? (One pass is fine.)
>
> Many thanks,
> -T


SATA 1, 150 MB/sec

# fdisk -l /dev/sdb

Disk /dev/sdb: 203.9 GB, 203928109056 bytes
255 heads, 63 sectors/track, 24792 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table



# date +%H:%M:%S; dd bs=1M if=/dev/zero of=/dev/sdb; date +%H:%M:%S
21:25:34
dd: writing `/dev/sdb': No space left on device
194482+0 records in
194481+0 records out
203928109056 bytes (204 GB) copied, 3874.7 s, 52.6 MB/s
22:30:10

Elapsed time 1:05:36