From: "William H. Geiger III" <whgiii@amaranth.com>
Date: Wed, 11 Jun 1997 23:11:21 +0800
To: cypherpunks@toad.com
Subject: Re: BAD ADVICE WARNING from Kent: Access to Storage and Communication
Message-ID: <199706111450.JAA01794@mailhub.amaranth.com>
MIME-Version: 1.0
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In <199706110235.VAA04670@manifold.algebra.com>, on 06/10/97 
   at 09:35 PM, ichudov@algebra.com (Igor Chudov @ home) said:

>Dr.Dimitri Vulis KOTM wrote:
>> Ray Arachelian <sunder@brainlink.com> writes:
>> > Passphrases can be memorized.  4mm DAT tapes hold several gigs and are
>> > tiny.  Ever see one?  Fits in your pocket.  It's smaller that an audio
>> > cassette. Fairly easy to guard, but, if your data is backed up in
>> > encrypted form (cyphertext), and not clear text, you don't even need to
>> > bother protecting the tape. (That is unless your backup software uses a
>> > weak cypher as most tend to do.)  [FYI: Your knowledge of tape
>> > technologies is severly lacking. 4mm tapes hold 2-4Gb.  Exabytes 5Gb-10Gb.
>> > Mamouth Exabytes (same size as 8mm camcorder video tapes, smaller than
>> > audio cassettes) hold as much as 40Gb in a very small form factor.]
>> 
>> I'm actually thinking of getting a pair of 4mm tape drives to replace
>> my existing backup system (very old drives that use DC 600As; only
>> .25GB / drive, pretty slow, no NT drivers; time to upgrade)
>> 
>> I wonder: if the data is well-encrypted, wouldn't it make the compression
>> pretty ineffective?

>You can compress before the encryption (if the encryption algorithm does
>not do compression).

>tar cvfz - /directory | Encrypt > /dev/ftape

>or something like that.

>Another thing to worry about is being able to at least partially restore
>data if one or several blocks get corrupted.

Well for backup purposes one would probably want to do their encryption on
a block size < file size. As an example for a 1M file you could encrypt it
as 10 seperate 100k blocks (or any suitable block size) rather than
encrypting the entire file in one block. I have programs on my system that
will do this for me but it would be best if all of this was built into the
backup software.

Myself I don't use tape. I use mirrored HD's and MO's & CD for short &
long term archives.

- -- 
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William H. Geiger III  http://www.amaranth.com/~whgiii
Geiger Consulting    Cooking With Warp 4.0

Author of E-Secure - PGP Front End for MR/2 Ice
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