<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Trevor Perring and Stephen Farrell have both referred to the design</div><div class="">goal of zero round trips. I just wanted to point out that in our</div><div class=""><a href="https://pomcor.com/techreports/M2MSec14.pdf" class="">secure channel design pattens</a> we easily achieve zero round trips, even</div><div class="">when the client and server have had no prior interaction, by</div><div class="">retrieving the server's long-term public key from the DNS rather than</div><div class="">from the server itself. (More precisely, we retrieve information</div><div class="">needed to compute the public key.) Which also has an obvious security</div><div class="">benefit besides achieving zero round trips.</div><div class=""><br class=""></div><div class="">This would be difficult to do in TLS, because the client would have to</div><div class="">retrieve the server's certificate chain, and the DNS may not be able</div><div class="">to supply that much data without hiccups. We do not have that problem</div><div class="">because our design patterns are based on identity-based cryptography,</div><div class="">and the amount of data to be retrieved is very small. Actually, in</div><div class="">small deployments no data needs to be retrieved at all, since the</div><div class="">server's public key is computed from its identity. In a global</div><div class="">deployment, the client retrieves the identity of the private key</div><div class="">generator (PKG) that it uses, and a chain of identities of</div><div class="">higher-level PKGs up to a root PKG. (PKGs are analogous to CAs.) The</div><div class="">public key is computed from the public key of the root PKG and the</div><div class="">identities of the other PKGs, but the public key of the root PKG does</div><div class="">not have to be retrieved because it is present in the client (just</div><div class="">like the public key of a root CA in the TLS PKI). So neither public</div><div class="">keys nor certificates need to be retrieved.</div><div class=""><br class=""></div><div class="">Francisco</div><div class=""><br class=""></div><div class=""><br class=""></div></body></html>