I am wondering if there are any readily available solutions for the following problem:
I have a ring-topology network with several devices connected to it, some malicious, some legitimate. I want to authenticate / establish a shared key between two legitimate devices, without the malicious ones finding out the key. There are no preshared secrets or certificates or anything, only this: During startup (and perhaps in regular intervals) I can exchange several messages between two trusted devices knowing for certain that the messages were sent by that trusted device (due to device-specific characteristic voltage spikes on the network).
Is this sufficient to establish a shared secret or key? I personally dont see a way but wanted to ask. Thanks!