[vonuebelgarten]

> So encryption isn't allowed, but is there any way to authenticate information sent over packet radio? Open communication has plenty of uses, but some of those can be spoiled by bad actors impersonating others.

You are not allowed to encrypt data on ham bands (this seems to happen Worldwide, it is also true here in Brazil), but there is no restriction on use of cryptographic primitives for authentication. But some countries (France, AFAIK) also require the protocol specs to be openly available, what should not be a problem in this field.

Digital signatures are Ok as long as the content of the message is not hidden (i.e. all listeners can receive and decode the information) and the transmission is identified (as usual in ham).