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More on packet radio encryption

This article was forwarded to you by [email protected] (Russell E. Whitaker):

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Path: eternity.demon.co.uk!demon!pipex!unipalm!uknet!doc.ic.ac.uk!agate!spool.mu.edu!sgiblab!public!grady
From: [email protected] ( )
Newsgroups: alt.privacy
Subject: packet radio encryption
Message-ID: <[email protected]>
Date: 11 Oct 92 19:41:12 GMT
Organization: BTR Public Access UNIX, MtnView CA. For info contact: [email protected]
Lines: 52

Bill Stewart ([email protected]) writes, in part:
   [...Unlike the AX.25 link protocol specified by FCC rules, the higher
   level protocols are not required to be plain-text...]

Do you have a reference for this?  And does this apply to the contents,
the protocols, or both?  (E.g. can you use a crypto-based presentation
layer protocol and plain-text payload, or vice versa?)


The definitive reference is Part 97 of the FCC rules
(available from the US Government Printing Office,
Washington, D.C.  20402.  Phone orders: 202 783 3238.
Ask for "Code of Federal Regulations" 47 CFR 80 to End.)

To summarize the rules, except for certain remote control
operation as space or repeater machines, nothing can be 
transmitted with the intent that the meaning be obscured.

Conversely, text compression, for example, is legal because,
although the plaintext is certainly obscured, it wasn't the _intent_
of the LZ or Huffman or whatever coding to conceal the

Likewise with UUencoding and a host of other compression/
error detection and correction schemes that incidentally
involutes the plaintext to some more efficient transmitted form.

Spread spectrum is treated somewhat more restrictively
since for that mode you may be required to produced the
logs and the content of the messages.  But not so for narrow-
band FM packet.

To sum up, using cryptography in general is prohibited.
(However, digital signatures are OK, even though based
on MD5 or SHA as long as the intent is not to _obscure the
meaning_ of part of the transmitted message.)

Clearly, though, the burden of proof is upon the FCC to show
that a particular message _was_ encrypted, since there
is _no_ theoretical, a priori way that an encrypted data
stream can be distinguished from one merely well compressed
or, just for that matter, random.

Of course you should verify this with an attorney if you are
troubled with fears of prosecution.

Grady Ward    KD6ETH/AA

Grady Ward  [email protected]com  Moby Lexicons

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