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Show HN: A new protocol for packet radio including ECDSA and compression

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Re: Show HN: A new protocol for packet radio including ECDSA and compression

#41

Post by someguydave »

aidenn0 wrote: post #35
vvanders wrote: post #30

Does this do any sort of FEC? One of the things that makes stuff like this tricky(and APRS in general) is that one flipped bit throws off the whole decode. From what I've seen out there would be a 40% improvement[1] in just base APRS if there was some form of basic FEC built into the protocol. Sadly most of "state of the art" is stuck back in the 80s. [1] http://eludium.stensat.org/mcguire/projects/FX-25/FX-25_perf..…

Does AFSK imply the use more than two frequencies? Using 4 or 8 frequencies and trellis modulating should get significant gain (i.e. using 4 frequencies and trellis modulating 1 bit per chip should be more robust than using just 2 frequencies).

AFSK, as used in amateur radio modems today, uses the Bell 202 modem standard, which is 2-ary FSK https://en.wikipedia.org/wiki/Bell_202_modem

Unfortunately, most folks on the VHF/UHF bands use FM radios with pre-emphasis and de-emphasis circuitry, so you would need to design a waveform that deals with those challenges.

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#42

Post by janoc »

emptybits wrote: post #7
Cyph0n wrote: post #2

Cool project! I have always been interested in the amateur radio scene. So encrypting amateur radio comms is illegal in the US? Is there a particular reason for this?

It's also illegal in Canada. With amateur radio "dying" as an interesting hobby (my opinion, but widely held) it is often speculated that if encryption was permitted in amateur radio communications, there would be quite a resurgence in interest. I predict a new generation would start to pick up the hobby and find untold uses (and abuses) for it.

If encryption was allowed, all that would happen is that people would start to use HAM bands as a cheap way to wirelessly connect to the internet or to build private communication links. Totally negating their purpose.

If you are after this (why would otherwise the lack of encryption be a problem for you?) there are both better bands and cheap hw to serve such commercial traffic needs (and, in fact, regulations in many countries explicitly outlaw use of HAM bands for traffic that can be better carried by other services - including the FCC in the USA - so even if crypto was legal, it would still be illegal).

And re amateur radio "dying" - that you don't hear anyone apart from a few old geezers chit chatting on a local repeater doesn't mean it is dying. There is a lot more to HAM radio than this - e.g. stuff like amateur radio satellites, APRS, all that SDR stuff, building digital networks, experiments with radar or even good old HF contesting. Or people simply enjoy building stuff and having the ticket lets them do it legally (some countries don't allow you to own HAM radio equipment without license).

HAM radio is far from dying, just it may not be what you imagine as a HAM radio - a bearded guy in his 60s ragchewing on HF ...

(I am a HAM operator myself)

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#43

Post by janoc »

emptybits wrote: post #40
brians wrote: post #13

Earlier quoted context omitted.

There are more hams in the US, and more active hams, than ever before. That's a funny sort of dying! Joe Taylor's work on below-the-noise signal extraction has revitalized shortwave: https://physics.princeton.edu/pulsar/k1jt/wsjtx.html , particularly at the nadir of the sunspot cycle. That's a funny sort of dying! Amateur satellites are accessible for $100 in parts: https://www.n2yo.com/satellites/?c=18 ; with the sa…

> There are more hams in the US, and more active hams, than ever before I apologize for repeating the doom and gloom then, because I know it can be self-fulfilling. The AARL has optimism but it also tells us net licenses are up http://www.arrl.org/news/more-than-30-000-new-ham-licensees-... A decentralized, no-carrier/ISP, disaster-tolerant medium for private communication would be amazing. I am not a licensed ham so…

If you want that, there are plenty of ISM bands and loads of cheap equipment you can use to build such "decentralized, no-carrier/ISP, disaster-tolerant medium for private communication" (aka internet ...)

HAM radio bands are meant for R&D work, learning and basically hobby stuff, not to replace internet or phone services - in fact, the regulations explicitly forbid such use.

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#44

Post by moftz »

vvanders wrote: post #30

Does this do any sort of FEC? One of the things that makes stuff like this tricky(and APRS in general) is that one flipped bit throws off the whole decode. From what I've seen out there would be a 40% improvement[1] in just base APRS if there was some form of basic FEC built into the protocol. Sadly most of "state of the art" is stuck back in the 80s. [1] http://eludium.stensat.org/mcguire/projects/FX-25/FX-25_perf..…

AX.25 has no FEC but there is FX.25 which is an encapsulation of the AX.25 packet with a preamble at the front and reed soloman at the end. But the issue is the speed of AX.25, 1200baud is dreadfully slow to be adding much onto the packet. The FX.25 protocol is a neat idea that allows for old TNC hardware to still be on the air. However, TNCs can be built with the cheapest of the raspberry pi clones so there really is no good reason as to why things can't progress to something like FX.25. There are certainly limitation to using 1200 baud AFSK but moving outside of the audio band, you could get some higher data rate but maybe loose some dB.

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#45

Post by janoc »

tlrobinson wrote: post #38
wedowhatwedo wrote: post #24

Earlier quoted context omitted.

Yes, if encryption was permitted, there would be a ton of interest...by commercial companies. Non-licensed users would out number licensed ones by huge amounts. It would put an end to amateur radio.

Requiring messages be signed by and for keys belonging to licensed amateurs might be sufficient to discourage abuse.

And how would you distinguish licensed users from unlicensed ones if the messages are encrypted?

Heck, the authorities have problems policing the bands even without having to deal with crypto.

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#46

Post by brians »

trothamel wrote: post #19
brians wrote: post #13

Earlier quoted context omitted.

There are more hams in the US, and more active hams, than ever before. That's a funny sort of dying! Joe Taylor's work on below-the-noise signal extraction has revitalized shortwave: https://physics.princeton.edu/pulsar/k1jt/wsjtx.html , particularly at the nadir of the sunspot cycle. That's a funny sort of dying! Amateur satellites are accessible for $100 in parts: https://www.n2yo.com/satellites/?c=18 ; with the sa…

Is there a good description of what those $100 in parts for satellite work are? Or better yet, something purchasable that's likely to work? I've been wanting to get into it, but I've never found a really accessible guide to getting started in satellite communication.

Sure! To talk to a satellite you need an antenna, a receiver, a transmitter, and maybe a computer—not for voice, but for text modes.

Arrow will sell you a great antenna: http://www.arrowantennas.com/arrowii/146-437.html , or you can google "tape measure yagi" and build an okay antenna.

Then you can get the transmitter and receiver together, in a package like the regrettable BaoFeng UV-5R: https://www.amazon.com/BaoFeng-UV-5R-Dual-Radio-Black/dp/B00... . This is a terrible radio. Their quality control is so bad that you sometimes commit a federal offense by pressing the transmit button—and for $100, you can't afford the test equipment to tell! So maybe use it as the receiver in a two-radio setup, and transmit with something like a Wouxun KG-UV9D.

A Kenwood TH-D72A is an excellent choice to do the transmitter and receiver jobs, but hundreds of dollars. A Yaesu FT-60 is a great choice too, but it won't have full duplex—so you can't be sure your signal is getting out without help.

To listen to a satellite you need even less: a crappy antenna and an RTL2832 USB software-designed radio: https://www.adafruit.com/product/1497

For all of these, you'll end up wanting miscellaneous coaxial cable and a bunch of ends. Hams tend to build up a library of crimpers and spare ends and such, so look to borrow from a friend or a club as you get started. The 75 Ω cable that's ubiquitous for television signals will totally work, but you'll have much less loss and much much less stress on components if you buy 50 Ω cable.

Why not try the tutorial at https://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weat... ? If that works, you can expand from there: the tutorial teaches you a huge amount about aiming at satellites and the physical work necessary to capture signals from space.

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#47

Post by tjohns »

giancarlostoro wrote: post #18
rtkwe wrote: post #17

Earlier quoted context omitted.

Yeah it's a bit of a compromise there it looks like. At the time the only reasonable codecs that existed were proprietary and allowing them with the stipulation that the patents be available on a 'reasonable and non-discriminatory' basis so anyone could make a commercial radio based on the codecs. At least with a proprietary codec with that patent restriction anyone can still go out and buy a compatible radio and jum…

Been wondering why some of the radios cost way too much and now I am left wondering how much cheaper they would be if those patented codecs were banned or forced to be open for implementation.

The AMBE-3000 vocoder chip (used for pretty much all of the digital modes, including D-STAR and DMR) retails for about $50, before volume discount.

Which is not a small mount of money, but isn't that bad given that most amateur radios (excluding the recent Chinese models) retail for ~$500, and commercial radios retail for $1,000+.

That said, I'm pretty sure everyone would prefer to move to Codec2, but the lack of hardware offerings is a problem. I'm looking forward to the day the first real SDR handheld transceiver comes out so this can be implemented by the open source radio community. It's clear that none of the radio manufacturers are interested in interoperability, much less adopting community standards.

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#48

Post by souterrain »

_9vzr wrote: post #31
leetbulb wrote: post #4

> With amateur packet radio anyone can pretend to be anyone else. With Chattervox, you can be sure you're chatting with the person you intend to. This is a great idea, for both the community and as a hobby project. Has there been any other attempts at similar protocols for amateur radio?

You can run just about anything over AX.25 since it's just the data link layer in the OSI model. You could run HTTP on top of IP on top of AX.25 with TLS/SSL message encryption turned off so you don't run afoul of FCC rules. The authentication would still be there but everything would be in the clear. You could also run IPsec with just the authentication field in the header, no encryption. Even if you didn't want to…

I owe my understanding of TCP/IP to running at 1200 bauds, half duplex, with poor collision detection.

http://www.ka9q.net/code/ka9qnos/

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#49

Post by tjohns »

trothamel wrote: post #19
brians wrote: post #13

Earlier quoted context omitted.

There are more hams in the US, and more active hams, than ever before. That's a funny sort of dying! Joe Taylor's work on below-the-noise signal extraction has revitalized shortwave: https://physics.princeton.edu/pulsar/k1jt/wsjtx.html , particularly at the nadir of the sunspot cycle. That's a funny sort of dying! Amateur satellites are accessible for $100 in parts: https://www.n2yo.com/satellites/?c=18 ; with the sa…

Is there a good description of what those $100 in parts for satellite work are? Or better yet, something purchasable that's likely to work? I've been wanting to get into it, but I've never found a really accessible guide to getting started in satellite communication.

In addition to the resources others have posted, I recommend picking up a copy of the AMSAT Getting Started book: https://www.amsat.org/product/2018-edition-of-getting-starte...

Re: Show HN: A new protocol for packet radio including ECDSA and compression

#50

Post by Evidlo »

someguydave wrote: post #41
aidenn0 wrote: post #35

Earlier quoted context omitted.

Does AFSK imply the use more than two frequencies? Using 4 or 8 frequencies and trellis modulating should get significant gain (i.e. using 4 frequencies and trellis modulating 1 bit per chip should be more robust than using just 2 frequencies).

AFSK, as used in amateur radio modems today, uses the Bell 202 modem standard, which is 2-ary FSK https://en.wikipedia.org/wiki/Bell_202_modem Unfortunately, most folks on the VHF/UHF bands use FM radios with pre-emphasis and de-emphasis circuitry, so you would need to design a waveform that deals with those challenges.

Also known as binary frequency shift keying (BFSK).
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