Re: [TLS] What would make TLS cryptographically better for TLS 1.3

Ralf Skyper Kaiser <> Sun, 03 November 2013 23:23 UTC

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Date: Sun, 3 Nov 2013 23:23:10 +0000
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From: Ralf Skyper Kaiser <>
To: Yoav Nir <>
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Subject: Re: [TLS] What would make TLS cryptographically better for TLS 1.3
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Hi Yoav,

i agree with the UI issue. That's the only use that I can see where
renegotiation is useful.

I would guess here that 99% of all TLS users (if not 99.99%) do not need
this feature.

The 99.99% of all users would have to carry the risk of complexity to
satisfy the need of the 0.01% of users.

There are hopefully other ways to satisfy the need of the 0.01% without the
99.99% of us having to take an extra risk (complexity). (Anyone? Ideas are

(ps when i'm speaking about complexity i do not mean the working hours it
would take to write the code [earlier replies by somebody indicated this]
but rather the security complexity [making mistakes and auditing a
process/procedures/... that is rarely used]).



On Sun, Nov 3, 2013 at 7:18 PM, Yoav Nir <> wrote:

> On Nov 3, 2013, at 9:03 AM, Ralf Skyper Kaiser <> wrote:
> > Hi,
> >
> > avoid renegotiation. It serves no purpose and only adds complexity. It
> is so much more secure to kill and re-establish the TLS if the counters run
> out instead of renegotiating.
> >
> Hi, Ralf
> The one use of renegotiation that I'm aware of, is for overcoming a UI
> issue in browsers. If you do a TLS handshake with mutual authentication (so
> the server sends a CertReq), the browser pops up a dialog box with all the
> certificates you might have. Website designers with to avoid that,
> especially on the welcome screen, so the web server does not send a
> CertReq. Instead, they present a welcome screen with a button or link that
> says "Login with certificates" Clicking that performs a regular SSL
> handshake (or does nothing at all if the connection is already
> established), but when the request comes in ("GET /login_with_certs
> HTTP/1.1"), the web server sends a HELLO_REQUEST, and in the resulting
> handshake it sends the CertReq, so the pop-up appears when the user *is*
> expecting it.
> I totally agree that renegotiation for rekeying is useless for people who
> are not doing DES-CBC and 3DES-CBC. It's even superfluous for them in most
> cases (you're pretty save doing 500,000,000 blocks, and that's 4 GB in
> 3DES. How many sites do you browse with 4 GB?  Maybe downloading stuff…)
> But before we can drop renegotiation from the standards, or recommend that
> implementors don't implement it, we need an alternate mechanism to upgrade
> from server-authenticated to mutually-authenticated within the same
> session. That is a real market need. How about allowing a CertReq sent from
> the server to the client in the middle of a connection, followed by the
> client sending a Certificate and Certificate Verify. For simplicity, we
> could always do that after the Finished, so that it's always
> Server-authenticated session when the Finished is sent.
> Yoav