Optimistic Encryption using TLS Signaling in the DNS

Document Type Expired Internet-Draft (individual)
Author Paul Hoffman 
Last updated 2014-10-12 (latest revision 2014-04-10)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Many Internet servers offer content in two transports: unencrypted, and encrypted with TLS. A user who accesses some content with a URL that indicates unencrypted (such as "http:") might prefer to get the content encrypted but doesn't bother to, or can't, change the URL to indicate this. This proposal allows Internet clients, particularly web clients and mail user agents, to do a DNS lookup to see whether they might expect content for a particular host to also be available under TLS. Using the DNS for this is much faster than attempting a TLS session that might time out or take many round trips in order to discover that the content is not available.


Paul Hoffman (paul.hoffman@vpnc.org)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)