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Re: [TLS] Killing Algorithms

Aaron Zauner <azet@azet.org> Fri, 03 April 2015 15:21 UTC

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Date: Fri, 03 Apr 2015 17:21:43 +0200
From: Aaron Zauner <azet@azet.org>
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To: Bill Frantz <frantz@pwpconsult.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] Killing Algorithms
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Hi,

Bill Frantz wrote:
> From my point of view, acceptable techniques include online code update
> and special messages which cause implementations to permanently cease
> using an algorithm, along with methods and procedures to ensure that
> these techniques actually work in the field.

As much as I like the idea, until someone proposes a sane method to do
so /online/ in the protocol, I don't think it makes a lot of sense to
add that to the document, it'll only confuse readers.

I can't think of a way a client or server could negotiate that a cipher
is deprecated. That'll cause downgrade attacks all over again, possibly
to the cipher that would by then be deprecated.

Aaron

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