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RE: Interesting One
From: "Jimmy Liang" <jimmy () jimmyland com>
Date: Wed, 30 Oct 2002 12:41:18 -0800

Interesting tho. How would the recovering software know if the data
you're retrieving comes from the 30th re-write, or the 29th?
You also have to consider that the data you're trying to recover isn't
the first data written to the disk.
So even if the atoms are not all aligned the right way, you wouldn't
know if that's because of the data from the 29th re-write, or the 30th. 

-----Original Message-----
From: Dan Darden [mailto:dld2517 () yahoo com] 
Sent: Tuesday, October 29, 2002 8:35 PM
To: John Orr; security-basics () security-focus com
Subject: RE: Interesting One


Think atomically.  There can be millions of atoms in a apace the size of
pin tip.  A write head need not turn every atom in a layer of magnetic
material one way or the other.  It only needs to turn just enough
one way in order for the read head to pick it up again.  If we talk
about a
layer of magnetic material that is just .0001" thick we are still
about layers upon layers upon layers (need I go on....) of atomic

It can be done!

Dan Darden.

Email dld2517 () yahoo com for your security
questions and information.

Hoax Info: http://hoaxbusters.ciac.org

"Everyday I beat my own personal record for
number of consecutive days I've stayed
alive" -- Author Unknown

-----Original Message-----
From: John Orr [mailto:JOrr () austinbank com]
Sent: Tuesday, October 29, 2002 12:15 PM
To: dadams () johncrowley co uk; security-basics () security-focus com
Subject: Re: Interesting One

  Personally, I think he is full of... hot air.

  Bits are either "on" or "off", "1" or "0".  If you change that pattern
(i.e. write over the same data area with a different sequence of bits),
the previous state of that field would not be determinable.  Granted,
may be some residual magnetic field left on a particular area that is
"0" that had been "1", but the converse would not be true.  There would
no residual field to read on an area that is now "1" that had been "0".

  Sounds like sales fluff to me.

  Anyway, that is my opinion, based on years of experience and a good
knowledge of physics.


John Orr
Austin Bank
903.759.3828 x2113
903.297.3094 fax
jorr () austinbank com

"Dave Adams" <dadams () johncrowley co uk> 10/28/02 04:06PM >>>
Greetings Folks,

I had an interesting conversation today with someone from FAST
Against Software Theft) They pretend not to be a snitch wing of the BSA.
Anyway, to get to the point, the guy that came to see me said that their
forensics guys could read data off a hard drive that had been written
up to thirty times. I find this very hard to believe and told him I
he was mistaken but the guy was adamant that it could be done. My
is, does anyone have any views on this, or, can anyone point me to a
of information where I can get the facts on exactly how much data can be
retrieved off a hard drive and under what conditions etc etc.


Dave Adams

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