[kerouanton]

Maybe (I'm also a HAM licensee) but making a device available on a IP network without any authentication and weak protocols such as telnet doesn't justify this.

[microcolonel]

I don't think there would be any issue with signing your datagrams, you just can't obscure the content of the communication or its purpose.

So yea on authenticity and access control, nay on transmitting ciphertext.