Article View: sci.crypt
Article #3876Re: Erasing magnetic media
From: Dennis L. Mumaugh
Date: Fri, 06 Nov 1987 15:44
Date: Fri, 06 Nov 1987 15:44
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2881 bytes
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
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!husc6!rutgers!ames!ucbcad!ucbvax!cbosgd!ihnp4!cuuxb!dlm From: dlm@cuuxb.ATT.COM (Dennis L. Mumaugh) Newsgroups: sci.crypt Subject: Re: Erasing magnetic media Message-ID: <1384@cuuxb.ATT.COM> Date: Fri, 6-Nov-87 10:44:16 EST Article-I.D.: cuuxb.1384 Posted: Fri Nov 6 10:44:16 1987 Date-Received: Tue, 10-Nov-87 07:10:09 EST References: <7566@reed.UUCP> <1175@cup.portal.com> <1945@crash.CTS.COM> Reply-To: dlm@cuuxb.UUCP (Dennis L. Mumaugh) Organization: ATT Data Systems Divison, Lisle, Ill. Lines: 50