Encryption and the Rules
Updated 14 Oct 2026. For the six VHF/UHF digital voice modes: DMR, D-STAR, System Fusion, P25, NXDN and M17. This is a plain language explanation, not legal advice. I'm not a lawyer.
The short answer
Digital voice is allowed. Encryption is not. A digital signal needs the right radio to hear it, but anyone can buy or build that radio. An encrypted signal needs a secret key, and only the people with the key can hear it. That is the line.
What the rule says
The rule is in the FCC's amateur radio rules, Part 97, section 97.113(a)(4). Among the things it lists as not allowed:
The key word is purpose. The rule does not ban encoding. Morse code is encoding, and so is every digital mode. It bans encoding that is done to keep others from understanding you. (The "except" part covers a few special cases, such as commands sent to amateur satellites. None of them apply to digital voice.)
Why the six modes are allowed
Each of these modes turns your voice into digital data so it can be sent over the air. That is encoding, but its purpose is to carry your voice, not to hide it. Anyone with a radio or receiver for that mode can hear you. There is no key and no password.
| Mode | Who can hear you |
|---|---|
| DMR | Anyone with a DMR radio or receiver |
| D-STAR | Anyone with a D-STAR radio or receiver |
| System Fusion | Anyone with a Fusion radio or receiver |
| P25 | Anyone with a P25 radio or receiver |
| NXDN | Anyone with an NXDN radio or receiver |
| M17 | Anyone with an M17 radio or receiver |
A scanner or plain FM receiver will not make sense of these signals, just as an AM radio cannot play an FM station. That does not make them hidden. It just means you need the right kind of receiver.
Why encryption is not allowed
Encryption scrambles the signal with a secret key. Someone with the same kind of radio but without the key hears nothing useful. That is encoding done to keep others from understanding, which is exactly what the rule bans.
Many DMR radios have an encryption or privacy setting, with names like Basic Privacy, Enhanced Privacy, ARC4 or AES. It is there because the same radios are also sold for business and public safety use, where encryption is allowed. On the amateur bands it must stay off. Even a weak privacy setting is still meant to keep people out, so it is still not allowed.
The voice codec question
A codec is the part that squeezes your voice into a small amount of data. Five of the six modes use codecs from one company, Digital Voice Systems, Inc. (DVSI):
- D-STAR: the original AMBE codec.
- DMR, System Fusion, NXDN and P25 Phase 2: AMBE+2.
- P25 Phase 1, the kind most hams use: IMBE, an older codec from the same company.
These codecs are privately owned, and radio makers pay DVSI a license to use them. Some people argue that a privately owned codec counts as hiding the meaning. Here is the plain situation:
- The codec is not a secret key. Every radio of that mode has it, and anyone can buy one.
- In 2019, New York University asked the FCC to widen the rule to cover messages that "cannot be readily decoded over the air for true meaning." The ARRL asked the FCC to dismiss that request, saying the existing rule already works.
- In 2023 the FCC ruled on other questions in that same proceeding and said it was taking no further action on the other issues. We found no FCC ruling that these codecs break the rule.
So this is an open argument, not a settled rule.
M17: the open codec
M17 uses a codec called Codec 2, created by David Rowe, VK5DGR. Codec 2 is open source, and the M17 standard itself is published openly under free licences. Anyone can read exactly how it works and build their own. So the codec argument above does not apply to M17.
One thing to know: the M17 standard also describes optional encryption, and it warns that encryption may not be legal in every radio service. On the US amateur bands the same rule applies as for DMR: leave it off.
Sources
- 47 CFR 97.113, eCFR and Cornell Law (the rule text)
- ARRL News: "FCC Asked to Clarify Amateur Rules Governing Encrypted or Encoded Messages" (Nov 2019) and "ARRL Asks FCC to Dismiss Petition..." (Dec 2019), plus ARRL's filed comments
- FCC documents DA 13-1918, DA 95-2106 and FCC 23-93 (WT Docket 16-239)
- DVSI product pages; Wikipedia, Multi-Band Excitation; dmrhub.ru; TrinityOS BayCon 2016 notes (which codec each mode uses)
- Radio Depot, Lasorsa and b3n.org on DMR privacy and encryption settings; AnyTone manuals and dealer pages
- M17 specification (m17project.org) and Wikipedia, Codec 2 and M17 (amateur radio)
- amateurradio.com, "Encryption is already legal, it's the intention that's not" (the codec argument)
A noncommercial hobby reference compiled by N6JET, gathered from public sources and shared freely for anyone interested in amateur digital voice.