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

mrex@sap.com (Martin Rex) Mon, 06 October 2014 20:24 UTC

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To: Hubert Kario <hkario@redhat.com>
Date: Mon, 6 Oct 2014 22:24:11 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
Archived-At: http://mailarchive.ietf.org/arch/msg/tls/S9xXVPSNLeyDXMPi5t1Y0NWCyv4
Cc: tls@ietf.org
Subject: Re: [TLS] I-D Action: draft-ietf-tls-prohibiting-rc4-01.txt
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Hubert Kario wrote:
>
>> My issue is with the IMHO bogus "MUST NOT" for servers.
>> Servers have no control over the client behaviour, and the current
>> proposal calls for an unconditional hard failure (equals to
>> "come back in clear text") rather than interoperating with an
>> RC4-based TLS cipher suites with installed base clients.
>
> thing is that only very specific clients do advertise only RC4,
> far less than there are RC4 only servers. Cloudflare saw on the
> order of 0.000002% of connections end up with RC4:
> http://blog.cloudflare.com/the-web-is-world-wide-or-who-still-needs-rc4/
> All from long obsolete clients.
> 
> Previously they saw on the order of 0.0009%:
> http://blog.cloudflare.com/killing-rc4-the-long-goodbye/


I'm not sure how representative that cloudflare statistic is.

But if this is anywhere near the real numbers, that the current
"MUST NOT" for server would be clear fear-mongering rather than
providing the target audience a sensible information about the
trade-off and realistic perspective on the insignificance of
the perceived threat.

-Martin