I don’t know if the government implication is as big as you think, as the US government has been doing secure satellite communications for decades and has already given SpaceX the contract for Starshield. So undoubtedly Kuiper would love a piece of the action but there is already competition and Kuiper is a bit late to the game.
Many key things the government buys need to have more than one independent source. This way Kuiper may be just in time.
SpaceX has proprietary info in practically all of their comm layers, so interoperability is not easy. The government probably did not buy full rights to the protocols. So the first step to Kuiper getting a piece of the pie is convincing the government that it is worth paying to license SpaceX’s comm standards so Kuiper can use them. That is not an easy task.
There are a dozen hypothetical ways that Kuiper might get a portion of government programs, but the fact is that SpaceX has been embedding themselves into the US government’s space infrastructure for years without competition, and has used that lack of competition to build up a bunch of technical hurdles to purchasing services from other contractors. For the past several years there has been no reason for the government to spend money and effort to prevent these hurdles because there was no other contractor that might be able to offer a similar service. So SpaceX has got a pretty sweet position right now, and Kuiper is going to have to invest heavily before the government changes course.
Starshield is a separate constellation for the US government and select allies only, and is built and launched by SpaceX.
How so? I'd imagine the datacenter terminal side downlink to be much more easily tappable than fiberoptics.
There are advantages in latency and potentially availability, but even there I would imagine fiber to win in an adversarial active jamming scenario.
I suppose in any realistic scenario we should assume that the enemy may be listening to all our communication at all times. This is the assumption behind such daily things as WPA3, SSH, TLS.
Jamming is a much more serious concern.
In the field it's a completely different story, of course – you can't always pull fiber (although it does appear in unexpected scenarios, such as fiber-operated UAVs or torpedoes).
Destroying fiber with a backhoe or an axe doesn't stop interfering when you stop digging or chopping though.
However, it's very easy to cut a fiber in a way that is hard to repair. Fishing trawlers do this all the time. In that sense, fiber can be "jammed" (sabotaged) much more easily than radio/satellite.
[1] https://en.m.wikipedia.org/wiki/Frequency-hopping_spread_spe...
Signal strength (satellites are power constrained) and distances involved are tough.
GPS uses frequency spreading too, and locally jamming that (even the military version with a secret/unpredictable spreading code) is trivial, for example.
Russia has some of the best EW chops in the world (after the NSA perhaps), and they struggled to successfully jam Starlink after some defensive work was carried out by SpaceX. They use Starlink in the “sea baby” USVs that attacked Crimea just last night.
https://tech.yahoo.com/general/articles/spacex-spends-signif...
I'm not saying that that's trivial against moving targets in a large area (especially if they can use directional antennas), but it's still very possible. GNSS jamming is a big concern of the militaries of the world, and there's currently somewhat of a renaissance of high-precision inertial navigation systems as a result.
Jamming a stationary satellite terminal, if you can get reasonably close, doesn't seem harder than cutting a fiber (although as a sibling comment has mentioned, jammers have the nice property that communication is restored once they're disabled, unlike damaged cables, so maybe the two can complement each other?)
With some satellites, you just point a dish at the satellite and get the same data everyone else gets. With more advanced ones, you have to be in roughly the same place as the intended recipient because the satellite has different antennas pointed in different directions. In either case, it's presumably encrypted data so what good is intercepting it?
Metadata security and availability are different concerns.
That might change once lasers or extremely tight radio beams can be used for ground stations, but for the latter you'd still need to make sure that nobody can get reasonably close to your ground stations, which might be possible for remote military bases, but probably not for AWS data centers.
If you have a dedicated circuit, you can send dummy data 24/7 to mitigate any traffic analysis. Even if you don't, you configure each link to send dummy data, so eavesdroppers can't do any traffic analysis without compromising the node itself.