Re: [TLS] Mail regarding draft-ietf-tls-tls13

mrex@sap.com (Martin Rex) Tue, 19 June 2018 23:07 UTC

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To: Ben Personick <ben.personick@iongroup.com>
Date: Wed, 20 Jun 2018 01:06:40 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/WtaXhi9J9x3Nm3MbVCjxLb8yBGU>
Subject: Re: [TLS] Mail regarding draft-ietf-tls-tls13
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Ben Personick <ben.personick@iongroup.com>; 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).


-Martin