Re: [TLS] New version of draft-ietf-tls-ecdhe-psk after the WGLC
<Pasi.Eronen@nokia.com> Thu, 02 October 2008 08:29 UTC
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Thread-Topic: [TLS] New version of draft-ietf-tls-ecdhe-psk after the WGLC
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From: Pasi.Eronen@nokia.com
To: badra@isima.fr
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Subject: Re: [TLS] New version of draft-ietf-tls-ecdhe-psk after the WGLC
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Mohamad Badra wrote: > > Dear Pasi, > >> The contents of the draft have changed quite a bit since version >> -02 (which was posted just before the Dublin meeting), and I have >> some comments about the changes: > > > In fact, we discussed adding SHA256 and SHA348 to the document to > avoid publishing several seperated documents; and if I recall well, > your recommendation was to do that in one single document. If the > group doesn't agree with this change, I will post the old version. I think having them all in a single document is better; it's the other changes in -03 I commented. > > It's a bit surprising that > > e.g. TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA, when negotiated in TLS > > 1.2, would use the TLS PRF with SHA-1 as the hash function. Note > > that e.g. TLS_DHE_PSK_WITH_AES_128_CBC_SHA (from RFC 4279) would > > in this situation use the TLS PRF with SHA-256. > > In this case, I would know where I can read that cipher suites > described in RFC 4492, when negotiated in TLS 1.2, will use the TLS > PRF with SHA-256. Do you refer to Section 5 of TLS 1.2? > > The same for TLS_DHE_PSK_WITH_AES_128_CBC_SHA. Yes, I'm referring to Section 5 of TLS 1.2. > > My suggestion would be to say that all these cipher suites can be > > negotiated with any TLS version; when used with TLS <1.2, they use > > the PRF from that version; when used with TLS >=1.2, they use the > > TLS PRF with SHA-256 or SHA-384. (In other words: they'd work the > > same way as the cipher suites in RFC 4492/4279/4785.) > > > > This change would probably allow us to remove the SHA-1 suites > > completely. > > With regard to version 2 of the document, only SHA-1 suites are > described. So why we need to do this step? I would ask it this way: if the document has SHA-256/384 based suites, why does it need the SHA-1 suites? (Cipher suites isn't one of those things where having more is automatically better.) > > Also, while I can understand combining AES-128 with > > SHA-256, and AES-256 with SHA-384, I'm not sure why we need to > > combine NULL encryption with three different MACs... > > In the case we are going to remove the SHA-1 suites with NULL > encryption, only 2 combinations will be available (if we keep the > logic of moving away from SHA-1 and towards stronger hash > algorithms, as RFC 5288 and 5289 do). Yes, but why do we need two combinations? What problem is solved by having two, instead of just one? Best regards, Pasi _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
- [TLS] New version of draft-ietf-tls-ecdhe-psk aft… Mohamad Badra
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Pasi.Eronen
- [TLS] RE: New version of draft-ietf-tlRE: New v… badra
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Mohamad Badra
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Mohamad Badra
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Pasi.Eronen
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Mohamad Badra
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Mark Tillinghast
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Alfred Hönes
- Re: [TLS] New version of draft-ietf-tls-ecdhe-psk… Mark Tillinghast