[bluGill]

You need some thing that the enemy cannot spoof. That means two way communication and a shared secret (public private key may count).

Then we need to ask what happens if communication itself fails? An enemy that knows you are doing this has incentive to jam Communications. Either you do nothing in that case because there might be something you can't communicate with, or you kill your own people

[CamperBob2]

An enemy that knows you are doing this has incentive to jam Communications.

The idea being that there is no communication to jam because the drone is fully autonomous. Given that, one needs a foolproof way for it to identify the enemy.

In this case the absence of communication would be what gives it permission to engage. Jamming the drone would not save you, but you could potentially make it attack its own forces if there happened to be any around at the time it comes for you. An IR beacon would make that very hard to accomplish.

[RealityVoid]

I think one way communication should be sufficient together with a shared secret. It's probably less reliable compared to two way communication, but it should satisfy the criteria. IR visual pattern propagation will respect this. You don't have radio spectrum that is too prone to jamming, and if the drones are visual navigation/targeting based, if they can see you to acquire the you as a target, they can identify you as a friend as long as you can ensure emitters are not occluded from your side.

It's not perfect, but it's cheap and it should work.

Give me a couple hundred k and I can probably build the prototype, haha.