Re: [TLS] Mail regarding draft-ietf-tls-tls13 (Martin Rex) Tue, 19 June 2018 23:07 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 2C873130FE4 for <>; Tue, 19 Jun 2018 16:07:04 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -6.9
X-Spam-Status: No, score=-6.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id VzZycwWRsGZJ for <>; Tue, 19 Jun 2018 16:06:57 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id DFF49130E35 for <>; Tue, 19 Jun 2018 16:06:44 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 419NrL0ZLGzHQ; Wed, 20 Jun 2018 01:06:42 +0200 (CEST)
X-purgate-ID: 152705::1529449602-0000081F-D6E48E2D/0/0
X-purgate-size: 1598
X-purgate: clean
X-purgate: This mail is considered clean (visit for further information)
X-purgate-Ad: Categorized by eleven eXpurgate (R)
X-purgate-type: clean
X-SAP-SPAM-Status: clean
Received: from ( []) by (Postfix) with ESMTP id 419NrJ6DPZzGpc5; Wed, 20 Jun 2018 01:06:40 +0200 (CEST)
Received: by (Postfix, from userid 10159) id C4A0D409C; Wed, 20 Jun 2018 01:06:40 +0200 (CEST)
In-Reply-To: <>
References: <>
To: Ben Personick <>
Date: Wed, 20 Jun 2018 01:06:40 +0200
CC: "" <>
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="US-ASCII"
Message-Id: <>
Archived-At: <>
Subject: Re: [TLS] Mail regarding draft-ietf-tls-tls13
X-Mailman-Version: 2.1.26
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 19 Jun 2018 23:07:04 -0000

Ben Personick <> wrote:
> (My apology for the long email, I did not have time to write a shorter one)
>  We are currently evaluating when to begin offering ECC Certificates
>  based cypto on our websites.
> Despite the advantages to doing this in TLS 1.2, there is a lot of
> push-back to wait until we "have to support it" once the TLS 1.3 draft
> is published, and the option to use it becomes available.

Honestly, why would you want to do this?

ECC/RSA Dual Cert setups a cryptographically a bad idea, and a real
nuisance for interoperability.

Elliptic Curve Crypto, when used with the design-flawed ECDSA digital
signature algorithm, might leak the private key within a few thousand
TLS full handshakes to a mere passive observer.

Support for EdDSA is somewhere between thin and non-existent still.

And for programmatic TLS clients, which take security serious, and
do not come with hundreds of public CA certificates preconfigured
as trusted, a sudden change of the TLS server certificate when
rearranging TLS cipher suites or when the underlying TLS implementation
starts include support for ECDSA certificates, can easily result
in a sudden unexpected loss of interop (missing trust).

Testing that you have the required trust properly configured for
*BOTH* TLS server certs is a royal pita, and _preparing_ for a TLS client
software update that adds support for ECDSA cipher suites is pretty
much impossible to test (unless you already have that implementation,
but that is not what I meant with preparing).