Re: [Cfrg] A little room for AES-192 in TLS?

Tony Arcieri <> Mon, 16 January 2017 18:09 UTC

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From: Tony Arcieri <>
Date: Mon, 16 Jan 2017 10:09:33 -0800
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To: "Paterson, Kenny" <>
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Subject: Re: [Cfrg] A little room for AES-192 in TLS?
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On Mon, Jan 16, 2017 at 9:37 AM, Paterson, Kenny <>

> Anyone else from CFRG have an opinion on this?

I would rate the chances of a related key attack against TLS as
"vanishingly small". The use of key derivation functions ensures keys will
not be related.

In practice, AES-192 is generally not used: AES-128 and AES-256 are used
almost exclusively. I think the general trend is to switch to AES-256 in
new systems.

Adding AES-192 ciphersuites sounds like an awful lot of additional
complexity both for specifiers and implementers for something I suspect no
one will ever use. Personally I would rather see that energy go into e.g.
post-quantum ciphersuites.

Tony Arcieri