<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=""><br class=""></div><div><blockquote type="cite" class=""><div class="">On Apr 16, 2016, at 4:48 PM, Tony Arcieri <<a href="mailto:bascule@gmail.com" class="">bascule@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="gmail_quote" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">While I'm not really a fan of DNSSEC, DANE TLSA records can contain a Domain-Issued Certificate where the entire certificate is provided in and authenticated via a DNS response.</div><br class="Apple-interchange-newline"></div></blockquote></div><br class=""><div class=""><div class="">A DANE TLS record may contain a certificate, but it may also contain</div><div class="">hash, to be matched against the certificate provided by the TLS</div><div class="">server. And section 10.1 of <a href="https://tools.ietf.org/html/rfc7671" class="">RFC 7671</a> recommends storing a hash in the</div><div class="">record rather than a certificate, precisely because DNS may have</div><div class="">trouble delivering even a single certificate due to the large size of</div><div class="">a certificate. (The RFC refers to UDP fragmentation, and to firewalls</div><div class="">not allowing the use of DNS over TCP rather than UDP.) Delivering a</div><div class="">certificate chain with multiple certificates would be even more</div><div class="">problematic.</div><div class=""><br class=""></div><div class="">By the way, while DANE requires DNSSEC, the paper does not. Using</div><div class="">plain DNS is all that's needed to achieve zero round-trips. And even</div><div class="">plain DNS provides a substantial security benefit, as briefly</div><div class="">discussed in section IV of the <a href="https://pomcor.com/techreports/M2MSec14.pdf" class="">paper</a>.</div><div class=""><br class=""></div><div class="">Francisco</div></div></body></html>