Re: [TLS] FFDHE and SHOULDs on usage
Hubert Kario <hkario@redhat.com> Mon, 20 April 2015 12:42 UTC
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From: Hubert Kario <hkario@redhat.com>
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Date: Mon, 20 Apr 2015 14:41:45 +0200
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Subject: Re: [TLS] FFDHE and SHOULDs on usage
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On Saturday 18 April 2015 05:10:52 Martin Rex wrote: > Daniel Kahn Gillmor wrote: > >> Groups are ordered based on client preference, noting the additional > >> ordering considerations in Section 6.1. > > > > Also, this rewrite says "ordered based on client preferences" but > > doesn't indicate which order based on client preferences: most preferred > > to least preferred or the other way around. It may be pedantic, but > > this is exactly the sort of pedantry that RFCs should include. > > Could we just scrap the "based on xxx preference" nonsense entirely? > > The sender of the list sends whatever it sees fit, and the receiver > of the list has the privilege to pick what ever the receiver believes > is most appropriate from the receivers point of view. > > I never understood why (a) such a silly suggestion was made for > the ordering of cipher suites in ClientHello and (b) why any TLS server > implementaion would care for the client's ordering rather than enforcing > the server preference. If the client does not want something, it must > not offer it. If the server does not want something, it must not pick it. If you have a relatively recent desktop CPU you don't care if you're using AES or ChaCha20. But if you're on a CPU which doesn't have a hardware acceleration for AES and is relatively slow (think mobile ARM), then you really would prefer ChaCha20 cipher over AES. So server should _consider_ client preference. And the clients should have an order which is sane. -- Regards, Hubert Kario 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
- [TLS] FFDHE and SHOULDs on usage Martin Thomson
- Re: [TLS] FFDHE and SHOULDs on usage Bodo Moeller
- Re: [TLS] FFDHE and SHOULDs on usage Martin Thomson
- Re: [TLS] FFDHE and SHOULDs on usage Daniel Kahn Gillmor
- Re: [TLS] FFDHE and SHOULDs on usage Martin Thomson
- [TLS] please review (was: Re: FFDHE and SHOULDs o… Sean Turner
- Re: [TLS] FFDHE and SHOULDs on usage Daniel Kahn Gillmor
- Re: [TLS] FFDHE and SHOULDs on usage Martin Thomson
- Re: [TLS] FFDHE and SHOULDs on usage Martin Rex
- Re: [TLS] FFDHE and SHOULDs on usage Andrey Jivsov
- Re: [TLS] FFDHE and SHOULDs on usage Thijs van Dijk
- Re: [TLS] FFDHE and SHOULDs on usage Hubert Kario