Frankly my gut feel is that Bitcoin transactions over Amateur radio is illegal, however I suspect it may be open to interpretation.

Amateur radio is NOT strictly non-commercial. For example a licensed ham CAN legally use an autopatch to order a pizza. A licensed ham CANNOT call his office on the same autopatch to retrieve his "business messages".

The kind of commercial that this might run afoul "Communications for hire or for material compensation, direct or indirect, paid or promised" or "Communications, on a regular basis, which could reasonably be furnished alternatively through other radio services." https://www.law.cornell.edu/cfr/text/47/97.113

Broadcasting in the open (i.e. not hiding the message) that Alice signed transaction X, unless Alice runs a business producing these transactions (i.e. Alice runs an exchange) - I am not seeing how that could be constructed as "commercial".

Intent behind "non-commercial" I believe was to avoid businesses jumping on the free resource and completely saturating channel with business stuff, where amateurs unlikely to do that, as there is no financial benefit. With that intent in mind, P2P transactions are "non-commercial" in my opinion.

> Broadcasting in the open (i.e. not hiding the message) that Alice signed transaction X, unless Alice runs a business producing these transactions (i.e. Alice runs an exchange) - I am not seeing how that could be constructed as "commercial".

The only way this can be considered non-commercial is if both station licensees involved in communicating the transaction have no commercial or pecuniary interest in the transaction. When it comes to cryptocurrency, this is a pretty fine line to walk, frankly, as both stations have to be able to prove that they are not performing business transactions or processing transactions for some business-related purpose.

Also, amateur radio operators are expressly forbidden from broadcasting within the ham bands except in a few very narrow cases such as calling CQ to initiate a contact and operating a beacon. All other communications must two-way communications.

> Intent behind "non-commercial" I believe was to avoid businesses jumping on the free resource and completely saturating channel with business stuff

Quite the opposite. Early radio broadcasters and wireless telegraph companies at first opposed any kind of regulation of the spectrum for all the same reasons companies still do today. But once it was clear that regulated spectrum management was here to stay, they fought very hard to keep as much of it as they could for themselves. Thankfully the government at the time recognized that radio hobbyists continued to make valuable contributions to the science and art of radio and was able to create the amateur radio service only after promising the corporate interests that amateur radio would not interfere with their business models. That is, amateurs cannot broadcast or (with narrow exceptions) make one-way transmissions, nor can they use their license to conduct communications "which could be reasonably furnished alternatively through other radio services." I interpret this to mean that amateurs cannot use their license and spectrum to conduct personal business where a cell phone would do.

> With that intent in mind, P2P transactions are "non-commercial" in my opinion.

Part 97 actually doesn't say anything about commercial or non-commercial, it prohibits "Communications in which the station licensee or control operator has a pecuniary interest." I am not a lawyer and I do not play one on the radio but I would argue that if somebody is sending you money over the radio and the FCC took notice, they would probably ask you to prove that the money wasn't in exchange for some service, which would violate the pecuniary interest clause.

I have no relevant knowledge or experience, and also not a lawyer to discuss it in any more details. But just small correction for you and others who might follow: such broadcast does not imply that both sides are involved in the actual transfer of money. In general case they are involved in the propagation of the transaction, and direct payment between two HAM participants is just one of the possible uses.

I know this is definitely true for specific 'ham' radio frequencies, but I've never found a clear answer as to whether it's also illegal to use encryption for commercial purposes over other frequencies like 2.4ghz on your own home-brew devices (assuming that you got them tested and licensed). Using a wireless router for commercial purposes obviously isn't illegal, but I'm not sure if 802.11 is some kind of exception?

> like 2.4ghz

2.4GHz is in the ISM band, and 47 CFR 15.247 specifically covers devices that use this range. Provided you stay within the specified limits, you have an implied license to use the band for those purposes.

There's no restriction on encryption in the commercial/business bands.

> assuming that you got them tested and licensed

This one is the kicker - it costs about $10-20k to get a device FCC certified, at least for part 90 devices, which is the industry I work in. A license to operate the devices runs around $500 (for ten years).

Interesting, thanks! That's for part 15 devices, which are exclusively devices operated without a licence, generally at low power.

Part 90 is a different beast, operating with licences, and at higher power limits. It doesn't surprise me the equipment licencing requirements are more intense.

Use of encryption (in the US, FCC part 97) is expressly prohibited as well. Get a commercial (Inmarsat, Iridium) satellite ground station if you want to do this sort of activity.

Bitcoin doesn't involve any encryption.

As long as the FCC interprets statute to not consider signed transactions as encryption (which is a possible outcome).

The ban is not on encryption per se (which, as you point out, could be confused with cryptography in general), but on attempting to obscure the content of messages. Obscuring message content is by no means a function of digital signatures.

For ECDSA you can’t provide a signature isn’t arbitrary data. The nonce is by definition not known, so it contains enciphered information.

That's true but not relevant here because the intent of the signatures is not to conceal the nonces.

I think you mean it can't be proven not to have 8 bytes of enciphered information.

But anyway, you can use a hash function to generate the 8 bytes of nonce.

You can’t prove you did without revealing the nonce, and therefor the private key.

You could reveal it once the transaction is used. If anyone really doubts your 8 bytes.

Correct, it involves a variety of cryptographic systems.

Ok, so why do they call it crypto?

It's shortened from "cryptocurrency", which derives from "cryptography". Bitcoin does use cryptography, including cryptographic hash functions (for summarizing data in a tamper-resistant way) and signatures (for attesting to authorship), but it doesn't make use of encryption, as the technology doesn't require concealing the content of any communication.

Encryption and cryptography are different things.

Encryption is a type of cryptography, but not all cryptography is encryption.

Yeah, or disagree with policy and law regarding who controls radio spectrum use. Short and long wave pirates serve a purpose and have a longstanding history of testing lines with defiance.

Citation needed.

https://en.wikipedia.org/wiki/Pirate_radio#References + https://sites.google.com/site/napiratehof/landing