Re: [TLS] I-D Action: draft-ietf-tls-prohibiting-rc4-01.txt

Yoav Nir <> Mon, 06 October 2014 20:12 UTC

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From: Yoav Nir <>
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Date: Mon, 6 Oct 2014 23:12:28 +0300
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Subject: Re: [TLS] I-D Action: draft-ietf-tls-prohibiting-rc4-01.txt
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On Oct 6, 2014, at 10:58 PM, Martin Rex <> wrote:
> Based on what we currently know about the weaknesses of RC4,
> unconditionally turning down clients will be ridiculously stupid
> in most situations, because for the vast number of scenarios,
> the weakness of the TLS RC4 cipher suites is not a threat.

Hi, Martin.

Both your implementation and mine have to deal with customers that run 4 or 5 year old software, and refuse to patch their systems. We know this is true, because TLS has a padding extension only because customers refuse to patch their systems.

So if the version that I am working on now is going to come out in 2015, some customers are going to run it in 2020. It should not include things that are likely to be ridiculous in 2020. So avoiding RC4 now is good. Avoiding SHA-1 in signatures is another good idea. Google can patch everyone’s Chrome in days. We are not so lucky.

So I think it should be MUST NOT for RC4. If some things can’t yet afford to comply with the new RFC, so be it. They’ll get there eventually.