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[TLS] Re: WG Consensus Call: Prohibit Key Share Reuse Between Connections

Ilari Liusvaara <ilariliusvaara@welho.com> Tue, 24 March 2026 15:58 UTC

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Date: Tue, 24 Mar 2026 17:58:27 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
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References: <92B7449C-F212-4A14-8852-58F8432FF131@sn3rd.com> <acIN2kRWLRSH_X_7@chardros.imrryr.org> <87bjgdy1fd.fsf@josefsson.org> <ddea35fe-0a18-4562-aa73-b9b6cd819360@tu-dresden.de>
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Subject: [TLS] Re: WG Consensus Call: Prohibit Key Share Reuse Between Connections
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On Tue, Mar 24, 2026 at 03:30:28PM +0100, Muhammad Usama Sardar wrote:
> On 24.03.26 11:19, Simon Josefsson wrote:
> 
> > Viktor Dukhovni<ietf-dane@dukhovni.org>  writes:
> > > FWIW, I still believe that the current SHOULD NOT (reuse ephemeral keys)
> > > is better than the proposed MUST NOT, however that's not a battle worth
> > > fighting.  It seems that the prevailing wisdom is to make the change,
> > > and no disaster will ensue if it is made.
> FWIW, the longer you use the ephemeral key, the higher the chance that it
> will be leaked. And leaking ephemeral keys can actually lead to disasters
> for security. So this change is actually protecting potential disasters from
> happening.

Even more important than duration of use is number of uses, as each use
exposes the key to side-channel, implementation error and fault attacks.
Especially in on-line protocols like TLS. In contrast, keys sitting in
memory unused are much less exposed.




-Ilari

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