The public key operations during setup are clearly useful for authentication against a possibly untrusted peer. What mechanism is used for key distribution? Rev

The public key operations during setup are clearly useful for authentication against a possibly untrusted peer. What mechanism is used for key distribution? Revocation? Is the main advantage over TLS in its use of a limited set of cryptographic primitives (as provided by NaCl), at the expense of flexibility? Any other advantages, such as decreased setup time? What about upgradeability -- does the protocol have the ability to roll in additional keys/exchange algos or ciphers as better ones become available? Of course, the more of these features you add, the closer you get to TLS. That being said, without these features (eg, if you need to basically upgrade your whole fleet just to update to a newer NaCl or to add keys as opposed to using a signed certificate mechanism), the advantage starts shifting towards even simpler approaches, such as spiped, which omits all the public-key ceremony in favor of a shared secret key.