Fresh from the Unless You’ve Been Living In a Cave, You’ve Heard of This department, there’s been much ado over the FCC Petition for Rulemaking seeking encryption for emergency communications. I won’t go into the details of the petition as you can read that several places elsewhere. Technically encryption on amateur radio bands is illegal. However, in reality the FCC has been letting it happen for years and the ARRL has turned a blind eye to it. D-STAR uses a proprietary vocoder that takes an analog voice signal and converts it into a data bitstream. The algorithm isn’t publicly documented and you can’t decrypt it, unless you buy a proprietary chip.
Some may quote § 97.309 (4)(b) which basically says one can transmit an “unspecified digital code” as long as the digital code is not intended to obscure the meaning of the communication. Presumably the people who created and use D-STAR don’t intend to obscure the meaning of the communication, so perhaps it is within the law.
So, say I create a new digital communication mode. It features a compression algorithm and I just happen to XOR the data stream with a 10 million bit pseudorandom bitstream to randomize it so a long stream of zeros or ones won’t screw up a modulator. I document the algorithm and the 10 million bit key on some corner of the Internet. It’s technically publicly documented, but in practice no one will go to the trouble of attempting to build a decoder. I’ve achieved encryption in a roundabout way. Whether my intentions were to obscure the meaning of the communications or make a modulator-friendly bitstream is anyone’s guess. But with the inaction over the D-STAR vocoder and the wording of § 97.309 (4)(b), intention rules the day. So while this debate over the petition is being framed in a discussion of encryption, it’s really the intent to obscure communications that’s at the heart of this.
I don’t have a horse in this emcomm race, but I’m not in favor of allowing obscuring messaging. If the FCC does allow it, others are going to want to use it for their noble causes, like preppers under the guise of “homeland security”.
(D-STAR is a registered trademark of Icom, Inc.)