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Comment by andruby | Hacker News Reader

I actually don’t know if they want to protect the data. I can imagine they might not want China or other countries listening in and potentially sending commands to the craft.

Does anyone know if there is typically encryption on the downlink? How about uplink commands? I guess we want those to be secured so only authenticated control can send commands

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Yes, CCSDS Magenta and Blue reference books mandate AES-256-GCM as a minimum for data encryption and mandate that encryption and authentication should be used, particularly for commands/uplink. Sliding scale of requirements based on application of course - your cubesat's imaging system is less critical than the flight termination system on a manned mission, for instance.

Fwiw, sat c&c is the one thing you're allowed to use encryption on the Amateur radio bands for.

how is that enforceable? you can't determine what the encrypted communication is.

Same as anything in amateur radio. There'll be a lot of hints at what you're doing from the shape of your broadcasts, and there's a lot of amateur radio enthusiasts that'll call the feds on you if they get a hint that you aren't following the rules.

radio enthusiasts are fans of the fed?

They're generally very into enforcing the FCC rules, and calling the feds is one mechanism for doing that.

Here's an ARRL article from 11-2016 (re the shutdown of 11 FCC field stations) which details plans and motivations.

https://www.arrl.org/news/fcc-special-counsel-laura-smith-sa...

In a more recent post (which includes good suggestions for experimenters):

> The ham bands aren’t full of whacked-out haters looking to get rid of everybody else, but hams are very accustomed to people using the bands without a license or not following the band plans, causing interference problems.

https://thesilicongraybeard.blogspot.com/2020/09/a-ham-radio...

Usually the 'self-policing' by hams (it's usually very effective) is done gently. They get that the frequencies are free of $$cost, and don't want to lose (any more of) them.

I highly suspect that China (and almost every other country) are not the issue. Chinese and the whole international scientific community will profit immensely from the data coming from James Webb, so I don't think the Chinese have any interest in sabotaging the project. More dangerous would be some average joe, somewhere who would try to mess with it for the lulz.

Or terrorist organizations with tech skills

Embarrassing the US is high value.

If somebody like China is caught sabotaging JWST the fallout could be immense. They would be accused of trying to hold back human progress, and I could easily imagine high profile Chinese scientists leaving the country and science institutions boycotting China. It's not worth the risk.

I also don’t think they would want to do this, but I think you’re overestimating the risk. Genocide, stealing the entire South China Sea, and threatening the sovereignty of other nations haven’t inspired such boycotts.

They actually understated the risk by incorrectly assessing where it would come from.

The primary risk would be that the US would hit back and attempt to sabotage something important to China (and with China's sprawling global interests now, there are a vast number of soft, highly exposed targets). The US Government can be quite vindictive depending on the context, it will hit you back if it can. The responsible agency wouldn't seek publicity for any successful sabotage, but China would know who did it and what it was for.

Schemes like that would involve not taking credit for it - just another example of US failure, not a success by China.

Or frame the average Joe for the lulz for political points.

(sorry, I'm just now reading into the drama with the fbi and gov. whitmer..)

There would have to be some sort of encryption or passkey or digital signature on commands, for sure. Otherwise some hobbyist in the middle of the Ocean on his yacht could be messing with the craft and taking pictures and there'd be no easy way to shut him down.

"Torpedo in the water!" would probably be sufficient.

The US government being able to discreetly torpedo everyone everywhere within what would have to be a few minutes at most, that would be pretty pretty scary. Imagine the number of drones they'd need to have deployed and armed at all times, and the potential for abuse.

I think you might just be trying to make this threat a much bigger issue than it really is. How many people do you really think will be trying to attack the JWST?

It is not necessary really.

There is unlikely any non-state actors[1] that has the ability to transmit signals to L2 . Just receiving signals even now (only 2 out of 30 days to l2) the OP used a 6 meter dish. Most of interplanetary mission signals are handled by the DSN.

Any sort of encryption will add both b/w requirements and compute requirements . The CPU/network budgets on such missions are very very limited. Every bit and cycle counts.

Finally standard encryption libraries, algorithms et al, are not likely suitable . I am no expert, but I have not read of any modern algorithms with very low network overhead + compute requirements designed for these kind of use cases, that is also secure from brute force or other attacks.

Mission risk is also a factor, even handshake failures can jeopardize the mission. It is one thing a website did not load because of TLS negotiation failures and $10 B mission overshot its orbit because handshake failures on the encryption layer.

[1] Threats from state actors for science missions is different category of concern, harder to quantify and with not much history of actual attacks. Collateral risks like from the ASAT Russian test to ISS, or in dual use missions would perhaps not apply here .Usually science teams collaborate well even if there is lot of tension in political sphere.

"It is not necessary really."

Authentication of commands to satellites is very, very necessary

Encryption !=authentication. OP was talking about encryption.

You could do authentication over plain text. For popular example http basic auth.

It is not recommended for regular use cases, but is not out of realm of possibility in satelite given the constraints.

OP was talking about digital signatures and a hobbyist taking command of the spacecraft. In other words authentication.

You said that was unnecessary and too taxing on constrained hardware. That is incorrect. Authentication is both necessary and not excessively taxing, when both considering the risk to the spacecraft's operation or even not considering it, since, as you said yourself, authentication schemes can be reasonably lightweight.

"Not out of the realm of possibility in satellites" What are you talking about? Of course it isn't! Authentication to satellites is recommended and implemented all the time, for obvious reasons. You think they risk a multi million dollar investment to save some clock cycles? How many commandeered satellites do you read about daily? Do you have sources to back up any of this?

I'd imagine the specs are rated and hardened for radiation first, as seen on all previous NASA satellite and probe missions before getting into the weeds of overhead and encryption.

I don't have any inside information but in my experience lurking in the amateur radio community the answer is 'it depends' and there is a lot of downlink that is not encrypted. This will get you into the graph:

https://twitter.com/usa_satcom

https://twitter.com/uhf_satcom

https://twitter.com/r2x0t

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