[bleepblorp]

Why would you assume the uplink isn't authenticated and/or encrypted, given that the downlink data has very little value but interfering with the uplink could disable the probe?

Spacecraft are power and compute limited. It's entirely possible the designers chose not to spend the resources to encrypt a downlink that isn't sending anything that needs to be kept secret. In contrast, it's reasonable to assume that the uplink is at least protected by a HMAC, because the consequences of an adversary exploiting the uplink are so great.

The Chinese are well aware that the US security establishment is petty enough to interfere with a scientific probe purely for its own amusement. They will have taken precautions to deter this.

[TeMPOraL]

That last remark was a bit uncalled for, but otherwise, you're spot on: this isn't a web API, there's no reason to assume symmetrical security measures on uplink and downlink. Keeping downlink in the open is actually pretty standard with satellites, but uplinks are almost always protected, because you don't want third parties to send commands to satellites or probes - be it adversaries or bored teenagers with a radio and a dish.

(And particularly in context of a high-profile mission like this, they definitely would want to keep telemetry open for third parties, to ensure their achievement is independently verified and recognized by the international community.)

[bleepblorp]

I don't see it as unjustified to point out that the primary risk actors in China's threat model will be the American armed forces and/or three letter agencies.

[TeMPOraL]

I didn't meant the "US armed forces" part, but the "them being that petty" one. Messing with a lunar mission would be risking an open conflict. I'm hoping they know better than to try that.