[Cryptography] New free TLS CA coming

Viktor Dukhovni cryptography at dukhovni.org
Wed Nov 19 13:16:47 EST 2014

On Tue, Nov 18, 2014 at 02:25:48PM -0500, Salz, Rich wrote:

> Initial drop of code and specs available here: https://github.com/letsencrypt 
> From https://letsencrypt.org/2014/11/18/announcing-lets-encrypt.html :
>       Let's Encrypt is a new free certificate authority, built
> on a foundation of cooperation and openness, that lets everyone be
> up and running with basic server certificates for their domains
> through a simple one-click process.

Since this is the cryptography list, we should perhaps discuss the
actual technology.

Is it reasonable to infer control of the domain based an the ability
to publish content at a chosen location on the domain's current
website?  Should any HTTP site hosting provider be able to
independently acquire new certificates for the domain?  Which CAs
are trusted to validate the current website?  Are http:// URLs
supported for initial bootstrap?

A non ad-hoc demonstration of both domain and site control is I
think a DNSSEC validated DANE TLSA RR attesting to the validity of
the public key:

    _443._tcp.www.example.com. IN TLSA 3 1 1 <sha256 pkey digest>

this allows domain owners to bootstrap (non-DANE) HTTP client
compatibility from a DANE record validated by the issuing CA.

Yes, other domain "control" demonstrations will likely be necessary
and acceptable, but they need to be chosen with care.

It is not always the case (or even desirable) that one can easily
automate either site content modification or DNS updates from the
edge server that terminates SSL connections and can use the signing

Making good choices of mechanism is important.  It can't just
be "a miracle":



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