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Re: [TLS] Ensuring consistent strength across certificate, ECDHE, cipher, and MAC

Hubert Kario <hkario@redhat.com> Wed, 23 March 2016 12:19 UTC

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From: Hubert Kario <hkario@redhat.com>
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Date: Wed, 23 Mar 2016 12:45:07 +0100
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Subject: Re: [TLS] Ensuring consistent strength across certificate, ECDHE, cipher, and MAC
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On Tuesday 22 March 2016 23:26:22 Dave Garrett wrote:
> X25519, secp256r1, X448, one of ffdhe3072 or ffdhe4096, and then
> lastly, ffdhe8192 and/or secp521r1 only as emergency backup
> (arguably, X448 belongs back here too)
> 
> I'd like to specify ffdhe2048 (~103-bit strength) as "MUST NOT" use
> for TLS 1.3+ and only support it for transition in older TLS. (this
> came up on-list a long while ago, but needs further discussion)

DHE gets prohibitive (computationally) rather quickly, and given that 
1024 only /may/ have been broken, a "SHOULD NOT" for 2048 with "MUST use 
ephemeral key share" is IMHO more appropriate

> I'd
> state secp384r1 (...) as "NOT RECOMMENDED" to bother with,
> but still permitted 

I'd say it is a tad bit too strong of a wording for the strongest curve 
supported by SChannel...

-- 
Regards,
Hubert Kario
Senior Quality Engineer, QE BaseOS Security team
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic

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