Comment by 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.