Re: Key backup (was: How do I know . ..)

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'Adam Shostack' was reported to have written:

> 	Putting the UPC's on things other than cards (such as books)
> makes it easier to hide in the open.  `UPC' stickers on, say, a few
> books are easier to miss than UPC stickers on index cards.

Exactly. If the intention is to keep them out in the open, then
making labels which resemble UPCs is preferred. However, if I'm
going to dig a hole in the ground at a secret location and bury my
barcoded key in a special container, a different format might be
indicated.

> 	Invisible ink draws attention to the correct UPC's once they
> know you're using it.  See Kahn for a discussion of secret inks being
> developed during the second world war. 

I'll do that, but I think you might be intermixing ideas. Pseudo-UPCs in
invisible ink wouldn't be a good combination. Pseudo-UPCs should 
probably be printed exactly like normal UPCs. If you want the "invisible
ink" process, it should probably blend into the ambient environment as
much as possible. Even if "they" know you're using secret ink, don't "they"
have to find the printed key first? How much work is required to check
every page of every book and every sheet of paper you might have access
to? You could mail your key anywhere in the world invisibly printed on 
the outside of an envelope. Better yet, send someone a special document
(wedding announcement, legal document, 21st birthday card, whatever;
the important part is to send something that the recipient will keep)
with your keyring invisibly printed on it. 

Variations on this theme (there are many) are encouraged. Have a friend
check out a library book and let you stamp your key somewhere inside. It's
the number of possible variations that make this seemingly impossible to
attack. Apologies if this "secret ink" stuff is way off base  ;-) .

Most people (myself included) would opt for the "split and
disguise" or "hidden/buried" key schemes where secret ink wouldn't add
much security.

> If you want to hide bits, they
> should be stripped of low entropy parts and hidden with a stego
> program.

The idea was to use something other than magnetic media. A new and
different optical encoding method could be devised to hide a key in a 
halftone, but the barcode example was offered as one possibility using
an existing standard. The basis for this thread was the perceived need
for a relatively simple key backup system that didn't require the active
participation of a whole hoard of people.


=D.C. Williams	<dcwill@ee.unr.edu>

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In article <199501182358.SAA29305@bb.hks.net>, you wrote:

> Variations on this theme (there are many) are encouraged. Have a friend
> check out a library book and let you stamp your key somewhere inside. It's
> the number of possible variations that make this seemingly impossible to
> attack. Apologies if this "secret ink" stuff is way off base  ;-) .
> 
> Most people (myself included) would opt for the "split and
> disguise" or "hidden/buried" key schemes where secret ink wouldn't add
> much security.

> 'Adam Shostack' was reported to have written:

> > If you want to hide bits, they
> > should be stripped of low entropy parts and hidden with a stego
> > program.
> 
> The idea was to use something other than magnetic media. A new and
> different optical encoding method could be devised to hide a key in a 
> halftone, but the barcode example was offered as one possibility using
> an existing standard. The basis for this thread was the perceived need
> for a relatively simple key backup system that didn't require the active
> participation of a whole hoard of people.

Pat Cadigan, in her novel SYNNERS, had the off-beat idea of having
crucial data encoded into graphical images and tattooed onto the skins
of beach bums.  

I've heard of worse ideas. . . .

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   abostick@netcom.com    | the compositor to make it unintelligible.
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Alan Bostick wrote:

> Pat Cadigan, in her novel SYNNERS, had the off-beat idea of having
> crucial data encoded into graphical images and tattooed onto the skins
> of beach bums.  
> 
> I've heard of worse ideas. . . .

She's a better novelist than an information theorist...

All the talk recently about data havens [secure storage variety] got
me to thinking. 

(In case you're wondering, I specified [secure storage variety]
becuase there seems to be some confusion, or at lest conflation, about
what a "data haven" does. Is it for selling illegal data publically?
Is it for storing sensitive material, privately? Something else?)

Anyway, for securely storing data that one wishes to be able to later
retrieve, but wishes thieves and authorities not to have, here are
some major possibilities:

1. The old stand-by. Keep copies of data at a friend's house. (This is
what I do, to guard against fires or thefts or ransackings by the
Thought Police.)

(Knowing where the stuff is stored is part of the "key" to getting it,
and only adds a few bits to the overall key lenth in most cases. That
is, not much security against a capable adversary, But fires are
usually pretty dumb, and cops not much smarter, so this works pretty
well.)

2. True secure storage, using a commercial service. Mineshafts, salt
domes, concrete buildings, etc. are commonly used for this. Corporate
records, etc. Pay a fee, store your files, etc. Of course, a subpoena
will get the data posthaste.

2A. Offshore secure storage, in a jurisdiction that will no honor
subpoenas form one's country. Lots of obvious issues here: bribery of
the vault, pressures applied locally, black bag jobs, etc.

3. Encryption, with either local or remote storage. 

3A. Encrypted, but local. This is by far the most common scenario, the
one most of us use all the time. Can the authorities force disclosure
of a key? I have a *lot* on this in my FAQ, so I won't repeat it here.
Basic conclusion: has not been tested, but it is unlikey that a
defendent who claims to have "forgotten" his passphrase, or who just
clams up, will get zapped for this, per se.

3B. Encrypted, offshore. Actually, this is similar to the above. If
the court can compell decryption, it can certainly compell retrieval
of files. And if it can't compell decryption, the files are no less
safe if stored locally.

(But I admit that the realities are not so simple. Offshore storage
offers some additionaal advantages. For one, "duress codes" that the
site owner in Belize that the person requesting the material, in LA,
is actually under duress. The site operator can then report back a
convenient "disk crash" and the authorities will be screwed. This
stratagem is harder to do cleanly in the U.S., for example, where the
site owner might be subpoenaed.)

4. Purloined Letter. Hide it in plain site. Steganography, in one of
your hundreds of DATs, or in GIFs and PICTs, etc. Without the key,
they won't know where it is.

(I've been pushing this since 1988, in postings on sci.crypt and
elsewhere. Romana Machado and others have implemented the image-based
version.) 

5. A variant is to use ftp sites. Encrypt the data and place it in an
ftp site that allows write access. Use remailers if you wish. Then,
your secret data is stored in encrypted, unidentifiable form on
someone else's computer, retrievable by you later.

(Lots of issues here. Our never-realized "anonymous anonyomous ftp"
capability could mean the storer would not even know what continent
the site was on.)

Well, these are just some of the ideas. Me, I stick to simply
encrypting sensitive files and keeping a couple of copies in safe
places. 

I don't think we ought to call these uses "data havens." Save the term
"data haven" for those places, in cyberspace or in real space, that
sell access to Nazi medical experiments, that sell illegal birth
control information, that buy weapons secrets, and so on. 

--Tim May


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From: tcmay@netcom.com (Timothy C. May)

   I don't think we ought to call these uses "data havens." Save the term
   "data haven" for those places, in cyberspace or in real space, that
   sell access to Nazi medical experiments, that sell illegal birth
   control information, that buy weapons secrets, and so on. 

I fully concur.  The connotations of the word "haven" imply activities
that ordinary people don't see themselves doing.  This means that
ordinary people won't generally use something called a "haven", even
if they might use exactly the same service called something else.

Eric