Out-of-band packet authentication by hardware means
I'm interested in the topic of using simple hardware means as a sort of out-of-band channel to authenticate packets. This question is rather academic in nature, I don't know of any system like this "in the wild". I can't seem to find much information about such solutions online either, but then again, I don't really know what this is called?
Consider Host X which sends cleartext packets to Host Y via an untrusted network. Let's say that the packets contain a payload and a random number. This random number is additionally transmitted out-of-band from Host X to Host Y by physical/unhackable hardware means. This could be done by a voltage level or hardware binary signals representing the random number.
Host Y will discard the packet if the random numbers don't match.
Is this a secure way to authenticate the packets, or are there flaws in my thinking? Confidentiality is not important.
+-----+
|Host |
| X |------------------------+
+-----+ |
| |
|Untrusted Ethernet / Hardware means to communicate a "one time secret",
|Network | i.e. random number or similar out-of-band
| |
V |
+-----+ |
|Host |<-----------------------+
| Y |
+-----+
