Michael.Chepponis@CMU-CS-C.ARPA (Mike Chepponis) (08/21/85)
I think it is noteworthy to look at section 97.69, Digital Communications. Paragraph (c) subsection 1: "In addition to the above provisions, the use of ANY <emphasis mine> digital code is permitted on amateur frequencies above 50 MHz, except those on which only A1 emission is permitted, subject to the following requirements: (1) Communications using such digital codes are authorized for domestic operation only (communications between points within areas where radio services are regulated by the U.S Federal Communications Commission), except when special arrangements have been made between the United States and the administration of any other country concerned. (2) <Deals with bandwidth restrictions. Notably: any BW permitted above 1240 MHz as long as sidebands stay in band.> (3) A description of the digital code and the modulation technique shall be included in the station log during all periods of use and shall be provided to the Commission on request. (4) When deemed necessary by an Engineer-in-charge of a Commission field facility to assure compliance with the rules of this part, a station licensee shall: (i) Cease the transmission of digital codes authorized under this paragraph. (ii) Restrict the transmission of digital codes authorized under this paragraph to the extent instructed. (iii) Maintain a record, convertible to the original information (voice, text, image, etc.), of all coded communications transmitted under authority of this paragraph." I'm not sure I understand the intent of these rules, but it would seem to allow user-to-computer communications using encryption PROVIDED that a record of all such communications was kept. Any opinions? 73, -Mike, k3mc -------
clements@bbnccq.ARPA (Bob Clements) (08/21/85)
Regarding Mike's comment that 97.69(c) permits the domestic use of any digital code, subject to certain restrictions: I think that the context of the rest of the section, and of the rulemaking in which that section was created, makes it clear that the use of the word "code" does NOT allow for encryption. It is used in the sense of American Standard CODE for Information Interchange (ASCII), or the Baudot code (or Murray code) or Hollerith code or whatever. In my comments filed to FCC during that rulemaking, I suggested that a group of hams might have a pile of Friden FIO-DEC flexowriters or some other totally obscure devices which use an oddball code. I said that it seemed to me to be in the public interest to let them use such devices, as long as there was no intent to be secretive about the communication and as long as they used a standard means of ID'ing their stations, such as Morse or ASCII or voice. It looks like they bought my argument. I think that's what this section, quoted by K3MC, means. 73, /Rcc, K1BC
Michael.Chepponis@CMU-CS-C.ARPA (Mike Chepponis) (08/21/85)
Bob, I believe you are right about the encryption issue - the purpose of encryption it to INTENTIONALLY obscure the meaning of the bits. In the beginning of 97.69, it says "These digital codes may be used for such communications as (but not limited to) radio teleprinter and other objects, transference of computer programs or direct computer-to-computer communications and communications is various types of data networks (including so-called 'packet switching' systems); provided that such digital codes are not intended to obscure the meaning of, but are only to facilitate, the communications, and further provided that such operation is carried out with other regulations set forth in this part." So, it seems like sending Huffman-coded text files (to reduce time &/or BW requirements) would be perfectly legal, but sending Huffman-coded text files for the purpose of encryption would be illegal. Does this seem like a gray area? -Mike, k3mc -------
wjc@ll-vlsi (Bill Chiarchiaro) (08/21/85)
It wasn't too many years ago that the only digital codes allowed for
Amateur transmission were International Morse, American Morse, and Baudot.
Then the FCC allowed ASCII, and eventually AMTOR and "any digital code
above 50.0 MHz."
I interpret those rules to have meant that before the allowance of
arbitrary digital codes, it would have been illegal to transmit raw binary
object code from your microcomputer over your packet-radio setup. It
would have been legal, say, to transmit ASCII-coded representations of the
hexadecimal characters that made up your object code. I believe the new
rules are intended to permit the efficient transfer of data. After all, it
only takes 8 bits of raw binary to send 8 bits of data as opposed to 16
bits of ASCII (i.e. two hex characters represented in ASCII). Also, the
new rules permit experimentation with techniques such as Huffmann (Huffman?)
codes for data compaction and convolutional codes for error correction.
The FCC has given us permission to experiment with modern techniques
with the intent of increasing the usefullness and efficiency of digital
communications. We must remember, however, that one of our rules (I don't
have the number handy) forbids us from taking steps to hide or obscure the
meaning of our transmissions. I know that there may be little chance of
ever being charged with a violation of this rule as a result of your use of
data encryption, although the probability might be about the same as for
those fellows who get caught running 10 kW. The point is, if the FCC asks
why it can't make heads or tails of your transmission, you better be able
to hand them a paper explaining how your technique furthers the efficiency
of Amateur communications. If you don't have a good answer, you may end up
reading about yourself in the Happenings column in QST.
Bill
N1CPKron@brl-tgr.ARPA (Ron Natalie <ron>) (08/22/85)
> I think that the context of the rest of the section, and of the rulemaking > in which that section was created, makes it clear that the use of the > word "code" does NOT allow for encryption. It is used in the > sense of American Standard CODE for Information Interchange (ASCII), or > the Baudot code (or Murray code) or Hollerith code or whatever. You left out MORSE.
karn@petrus.UUCP (Phil R. Karn) (08/24/85)
We are fortunate that the encryption prohibition is worded the way that it is, with the key point being whether there is intent to obscure the meaning of a message. This allows us complete freedom to experiment with any sophisticated, nonstandard encoding method we choose without worrying about difficult it might be to monitor. As long as it serves some valid communication purpose other than hiding the message, we're OK. A case in point is the 9600 baud FSK modem design by Steve Goode, K9NG. Steve's biggest problem was to get rid of the DC components in a data stream; this simplifies the design greatly, since you can use AC coupling and not worry about things like op-amp offsets, crystal tolerances, etc. One approach is Manchester encoding, but this effectively doubles the bandwidth required for the signal. Steve's solution was to add a pseudo-random stream to the data at the transmitter, removing it at the receiver. In the commercial world, this technique is commonly known as "bit scrambling", a term with unfortunate connotations. (The technique DOES resemble an encryption system, although one based on a linear feedback shift register would be very easy to break.) However, since Steve's intent is not to obscure the meaning of a message but rather to simplify the hardware design, it is acceptable. (Of course, it also helps that he published the algorithm and encoding/decoding circuit at the last ARRL packet radio conference.) Phil