🚀 go-pugleaf

Others may be interested.... The actual requirement is that the media
be written with at least 100 alternating 1/0 bits. i.e 11111 00000 11111,
etc...  Some media cannot be declassified. If memory serves, the old (still
in use in the Minuteman system) core memory had to be destroyed.

In article <1175@cup.portal.com> Kenneth_R_Jongsma@cup.portal.com writes:
>Others may be interested.... The actual requirement is that the media
>be written with at least 100 alternating 1/0 bits. i.e 11111 00000 11111,
>etc...  Some media cannot be declassified. If memory serves, the old (still
>in use in the Minuteman system) core memory had to be destroyed.

I am interested in 'Why' 100 alternate 1/0 writes will not declassify some
media.  It seems to me that after 5 or so random 1/0 writes the original
data would be so far gone that retreival by any means is impossible.

Enlighten me.

--Keith

-- 
ARPA: crash!ag@nosc.mil                                 INET: ag@crash.CTS.COM
            UUCP: {cbosgd, hplabs!hp-sdd, sdcsvax, nosc}!crash!ag

In article <1175@cup.portal.com> Kenneth_R_Jongsma@cup.portal.com writes:
>Others may be interested.... The actual requirement is that the media
>be written with at least 100 alternating 1/0 bits. i.e 11111 00000 11111,
>etc...  Some media cannot be declassified. If memory serves, the old (still
>in use in the Minuteman system) core memory had to be destroyed.


I believe that once a media has been used for classified data, it can not
be re-used for unclassified data.  To dispose of, it must be destroyed.
It is quite easy (given the proper equipment) to recover information that
has be written over several times.

In article <6964@pur-ee.UUCP> 3ksnn64@pur-ee.UUCP (Joe Cychosz) writes:
>It is quite easy (given the proper equipment) to recover information that
>has be written over several times.

Could you enlighten us with the details?  There is great commercial
potential in being able to recover files that have been accidentally 
overwritten.

---
Larry Colton                      {ihnp4,pyramid,qantel}!ptsfa!pbhyd!lc
Pacific * Bell                                                San Diego

In article <1945@crash.CTS.COM> ag@crash.CTS.COM (Keith Gabryelski) writes:

>I am interested in 'Why' 100 alternate 1/0 writes will not declassify some
>media.  It seems to me that after 5 or so random 1/0 writes the original
>data would be so far gone that retreival by any means is impossible.
>
>Enlighten me.
>

Small signal analysis can be used to recover "each layer" of data written.

In article <1029@pbhyd.UUCP> lc@pbhyd.UUCP (Larry Colton) writes:
>In article <6964@pur-ee.UUCP> 3ksnn64@pur-ee.UUCP (Joe Cychosz) writes:
>>It is quite easy (given the proper equipment) to recover information that
>>has be written over several times.
>
>Could you enlighten us with the details?  There is great commercial
>potential in being able to recover files that have been accidentally 
>overwritten.

There tends to be small differences between the signal levels as
a result of the previous data.  A 1 which overwrites a 1 is
commonly a small amount stronger than if the previous data was a
0.  Careful signal analysis can attempt to remove the obvious
data by subtraction. The result is the previous data.  If the
data is valuable enough the effort is worth it.  Also there is
some information on the edge of the track that is effectively
unchanged because of the minor alignment differences from one
write to the next.  Using heads of slightly different sizes and
alignments can increase the signal to noise (data) ratios.  In
any case the last data is obvious which greatly simplifies its
removal from the signal.

In general the above is smoke. Although I have been told that
some companies do provide a service recovering data from various
types of media.  The real security problem is if ANYTHING is
permitted out of the room.  How do you detect someone
removing/trashing a tape or disk-pack that has been erased with
encrypted (their code) data or written/erased with reduced
current to the heads? It might look ok but out goes national
security.  When I was in school someone picked up some surplus
(USAF) 1/2 inch tapes which we were going to split for audio use.
We hung them on the CDC and they were not all blank.  Since it
was the very late 60's we were surprised, but not surprised that
nothing made sense.

In fact on many installations the dump and trash bin is one of
the most securely guarded and managed areas.

I do not know of any service companies by name that recover data
but contact someone at a Big Blue/Bank data processing center for
pointers.  If you cannot get in try a suit and a job application.
Brush up on COBOL RPG and such, big well run DP shops are worth a
visit.  The key words are "well run", not Big or Blue.

Thanks for the soap



Thomas P. Mitchell (mitch@stride1.Stride.COM)
Phone:	(702) 322-6868 TWX:	910-395-6073
MicroSage Computer Systems Inc. a Division of Stride Micro.
Opinions expressed are probably mine. 

In article <6964@pur-ee.UUCP>, 3ksnn64@pur-ee.UUCP (Joe Cychosz) writes:
> In article <1175@cup.portal.com> Kenneth_R_Jongsma@cup.portal.com writes:
> >Others may be interested.... The actual requirement is that the media
> >be written with at least 100 alternating 1/0 bits. i.e 11111 00000 11111,
> >etc...  Some media cannot be declassified. If memory serves, the old (still
> >in use in the Minuteman system) core memory had to be destroyed.
> I believe that once a media has been used for classified data, it can not
> be re-used for unclassified data.  To dispose of, it must be destroyed.
> It is quite easy (given the proper equipment) to recover information that
> has be written over several times.

At the Concourse Computer Center at MIT, most of our tapes were used tapes.
Many of these had little stickers saying "SECRET", which had been blotted out
with a magic marker.  Presumably, there are ways to PREVENT the recovery of
information that has been on the tape.

--
John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101
...!decvax!frog!john, ...!mit-eddie!jfw, jfw@eddie.mit.edu

"Cutting the space budget really restores my faith in humanity.  It
eliminates dreams, goals, and ideals and lets us get straight to the
business of hate, debauchery, and self-annihilation."
		-- Johnny Hart

In article <1029@pbhyd.UUCP> lc@pbhyd.UUCP (Larry Colton) writes:
>>It is quite easy (given the proper equipment) to recover information that
>>has be written over several times.
>
>Could you enlighten us with the details?  There is great commercial
>potential in being able to recover files that have been accidentally 
>overwritten.
>

There is a residual of the original data still present.  Small signal
analysis can be used to recover the original data.  Obviously the more
times the tape is written over, the harder it is recover the intended
data.

In article <1945@crash.CTS.COM> ag@crash.CTS.COM (Keith Gabryelski) writes:
>In article <1175@cup.portal.com> Kenneth_R_Jongsma@cup.portal.com writes:
>>Others may be interested.... The actual requirement is that the media
>>be written with at least 100 alternating 1/0 bits. i.e 11111 00000 11111,
>>etc...  Some media cannot be declassified. If memory serves, the old (still
>>in use in the Minuteman system) core memory had to be destroyed.
>
>I am interested in 'Why' 100 alternate 1/0 writes will not declassify some
>media.  It seems to me that after 5 or so random 1/0 writes the original
>data would be so far gone that retreival by any means is impossible.
>
>Enlighten me.
>
Having a modest part in the original decisions that  lead  up  to
the policy I will attempt to answer .....

Way back when, our group had a problem with  computers  that  ran
classified  programs (and with classified data).  What to do with
the defective memory which  in  those  days  were  magnetic  core
based.

Certain studies said [ deleted ] ....

So the final policy was that if one over wrote the data with  100
cyles of ones and zeros (alternating) any data would be so buried
in the ramdom molecular noise that ....  This  was  for  magnetic
cores.  Similar behavior was approved for tapes using VERY strong
degaussing methods.

But then some one asked the question: "That means  I  could  mail
the  tape  to  the  Russian Embasy, then?" And the powers that be
looked  pale.  So,  the  compromise  was  reached:  treat  it  as
unclassified but don't EVER let it leave safe handling.

The effect  was  to  allow  it  to  be  handled  administratively
unclassified and stored that way.

But when sending a tape out of the "compound"  one  must  certify
that the tape has NEVER had any classified data on it.  Hence our
penchant for sacrificing virgins [tape that is] to the computer.

Disks are a diferent story as the write heads tend  to  splatter.
Also only certain tape degaussers are approved.

BTW:  I once did  send  some  one  a  tape  and  they  were  VERY
disappointed  that  it  wasn't  used,  with intereresting goodies
following the two tape marks.
-- 
=Dennis L. Mumaugh
 Lisle, IL       ...!{ihnp4,cbosgd,lll-crg}!cuuxb!dlm

/ hpcvla:sci.crypt / john@frog.UUCP (John Woods, Software) /  2:33 pm  Nov  4, 1987 /
In article <6964@pur-ee.UUCP>, 3ksnn64@pur-ee.UUCP (Joe Cychosz) writes:
> In article <1175@cup.portal.com> Kenneth_R_Jongsma@cup.portal.com writes:
> >Others may be interested.... The actual requirement is that the media
> >be written with at least 100 alternating 1/0 bits. i.e 11111 00000 11111,
> >etc...  Some media cannot be declassified. If memory serves, the old (still
> >in use in the Minuteman system) core memory had to be destroyed.
> I believe that once a media has been used for classified data, it can not
> be re-used for unclassified data.  To dispose of, it must be destroyed.
> It is quite easy (given the proper equipment) to recover information that
> has be written over several times.

At the Concourse Computer Center at MIT, most of our tapes were used tapes.
Many of these had little stickers saying "SECRET", which had been blotted out
with a magic marker.  Presumably, there are ways to PREVENT the recovery of
information that has been on the tape.

--
John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101
...!decvax!frog!john, ...!mit-eddie!jfw, jfw@eddie.mit.edu

"Cutting the space budget really restores my faith in humanity.  It
eliminates dreams, goals, and ideals and lets us get straight to the
business of hate, debauchery, and self-annihilation."
		-- Johnny Hart
----------

I seem to recall that heating a magnetic material above its Curie point
will _totally_ randomize the fields. If so, the next question is "is the
Curie point for a floppy (or tape) high enough to damage the media?"

If the answer is no, then I can see the labels now...
	"to declassify, place media in 350 degree oven for two hours"
:-) :-)
-- 
Leonard Erickson		...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I used to be a hacker. Now I'm a 'microcomputer specialist'.
You know... I'd rather be a hacker."

Aargh!  There is not just one definite regulation covering this.
AR380-380 is the Army's main Regulation covering computer security,
but there are other documents too, some classified and some not.
Generally disk packs, magtapes, MOS memory, etc. used for routine
SECRET data storage can be overwritten a sufficient number of times
with alternating patterns; otherwise the media can be "degaussed",
although it may mean sending your media via authorized courier to
some place with appropriate facilities.  Some categories of
information (e.g. SI) are considered too sensitive to take any
avoidable risk, and for them the pattern overwriting method is
unlikely to be authorized.

The only safe thing to do is to consult your local ADP security
office.  If they don't know the regs, it's their job to find out.

Seems like the method of choice for making sure the data will never be
read again is a flamethrower |-)...

My point is that it seems like destroying the things would be better
than any erasing method.  Or do I have a very bad idea of how much tape
costs?

James Moore
..!ucbvax!leggatt!jmm

	Ocus ni rabe isin bith ni dognethe
	n-eret sin leu acht cluchi
	ocus cheti ocus anius ocus aibinnius
	ocus longad ocus tomailt, conid de sin
	atat na trenae samna sechnon na hErend."
	     -as an sceal _Seirgligi Con Culaind inso sis ocus oenet Emire_ 

I believe that the Curie point for most commonly used media is 200
Celsuis - which should be hot enough to destroy the mylar of tapes or
floppies. As for hard disks, once it is no longer magnetic, you will
have a hard time writing new data onto it, won't you?

						Eric

In article <456@ucdavis.ucdavis.edu> hildum@iris.UUCP (Eric Hildum) writes:
<
<I believe that the Curie point for most commonly used media is 200
<Celsuis - which should be hot enough to destroy the mylar of tapes or
<floppies. As for hard disks, once it is no longer magnetic, you will
<have a hard time writing new data onto it, won't you?
<
<						Eric

I'm not so sure that that is high enough for damage but it is probably
too close. I _do_ know that there is a high speed tape duplication system
that heats the media past the Curie point and then cools it in "contact"
with the media to be duplicated. As the media cools it will _easily_
align its domians with any applied field.

As for hard disk media, the material becomes magnetizable after it is cooled.

-- 
Leonard Erickson		...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I used to be a hacker. Now I'm a 'microcomputer specialist'.
You know... I'd rather be a hacker."

In article <456@ucdavis.ucdavis.edu> hildum@iris.UUCP (Eric Hildum) writes:

+I believe that the Curie point for most commonly used media is 200
+Celsius - which should be hot enough to destroy the mylar of tapes or
+floppies. As for hard disks, once it is no longer magnetic, you will
+have a hard time writing new data onto it, won't you?

Cool it!!


-- 
	carl lowenstein		marine physical lab	u.c. san diego
	{ihnp4|decvax|dcdwest|ucbvax}	!sdcsvax!mplvax!cdl

Oops - 

I guess it has been to long since I looked at magnetic memory devices.
gamma Fe2O3 converts to alpha Fe2O3 at a temperature of 400C; which I
was remembering as the Curie point for some strange reason.  Actually,
the idea of heating the recording media to erase it might work for
CrO2 which has a Curie point of 120C.

				Eric

Heating a disk pack past its Curie temperature will erase the
factory-recorded timing information on the servo tracks, which
the drive depends on to mark track and byte boundaries.
(Low-density disks like floppies don't have servo tracks).

Heating a whole Winchester drive past the Curie temperature
will demagnetize the permanent magnet in the head actuator.

Don't heat a hard disk unless you're going to incinerate it.

Don Speck   speck@vlsi.caltech.edu  {amdahl,scgvaxd}!cit-vax!speck