You could look for resources that cover digital HAM radio operation. They should have some stuff about the basics of voice encryption. Most of it is not secure until you get to high-end stuff like Motorola AES 256. Some of this 'encryption' is just privacy codes (cell networks are not encrypted but use digital privacy codes I think).
Once you digitize the voice, then it should be pretty much regular encryption.
https://www.amateurradio.com/encryption-is-already-legal-its...
Like I said in my original post, you can look into encryption in the amatuer bands. This article is one example. If you've taken encryption courses then you know that XOR can be a cipher, it's just not secure. The same way a lock on your shed is only going to keep curious people out and not real criminals, the same can be said for lesser forms of encryption.
Please look into Kenwood AES/DES models that operate in the VHF/UHF amatuer bands if you still have any doubts about the use of encryption. There are various 40, 56, etc bit encryption schemes as well.
Over on HF, digital modes like FT8 are quite popular. You will never be able to decode that without a computer, but that doesn't make it illegal (or encrypted). The algorithm is well defined and it's ~100x more bandwidth efficient than SSB voice.
Kenwood sells AES radios for non-amateur communications. It's perfectly legal for non-amateur licensees to encrypt their radio links. Your cell phone is doing it right now!
Yes, you can use those on the amateur bands if you want. It's against the rules. The reason amateur radio exists is because we follow the rules. It can all disappear overnight if you violate them. There are a few well-known bad apples that make it harder for all of us. It's not to be encouraged.
For a long time the audio codec was only available in a chip (technically a readout protected microcontroller). There are patents on the audio codec, but they didn't disclose enough of it to decode it, only enough to make it unlawful for other people to publish compatible implementations (which, of course, kept the resources available for reverse engineering low).
For a while I contemplated selling bespoke custom versions of Opus as a bit of performance art under licensing where the first copy cost $500 and all further copies cost $1,000,000 with some marketing copy about keeping lids off your repeaters. ... just to see how the FCC would react.
Considering that they let AMBE use get away with it, as the old joke goes: We've already established what kind of licensing regime they'll permit-- pay to access encrypted audio-- my performance art differed only by the price.
:)
> The reason amateur radio exists is because we follow the rules. It can all disappear overnight if you violate them. There are a few well-known bad apples that make it harder for all of us. It's not to be encouraged.
Personally, particularly on bands above 70cm, I think the prohibition against encryption is killing amateur radio. The lack of encryption for signals that would be naturally point to point anyway and disturb no one inhibits a lot community use, and the relative non-usage of these allocations risks use losing them.
I'd much rather see a rule that allowed encryption on 33cm+ subject to the constraint that stations have to be identified, non-profit in nature, cooperate with local coordination, and act as secondary users to non-encrypted uses.
Yes, I think it is reasonable, although I don't know what bands to have that on, and of course it should not be interfering with non-encrypted uses.
(And perhaps the same rule should be applied to proprietary codecs, too, so that they don't overload the radio with proprietary codes that you cannot figure out how to decode.)
As an American this sort of sentiment is absolutely depressing to see. It seems to be incredibly common in a number of areas - radio, flight, and chemistry, to list just a few. I can only hope access to unencumbered computers doesn't fall victim to the same.
WTF happened to our supposed ideal of freedom?
I'm not advocating that they use true encryption in the ham bands, but it does exist. As I said before, there is information out there about how voice is digitized, how psuedo or weak encryption works (DMR, 40 bit, 56 bit), and then you can use standard encryption practices to encrypt it.
The OPs question was about where he can find technical info on encrypting voice communications and I said this would be a good starting point. This is a valid contribution to his question. I am sorry if you do not believe that weak encryption (where you know all possible keys, or the keys are small) is not encryption.
Yes they do. Decades ago they didn't. Today there are devices that use active attacks to downgrade the encryption by impersonating a base station.
It's also possible to crack the encryption used by GSM, but I believe the base station impersonation attacks are much more common.
I believe they are not encrypted, but use a few thousand channels on a trunked system.