RE: [Hokeyp] [Emu] Re: MSK but no EMSK

["Narayanan, Vidya" <vidyan at qualcomm.com>]

Hi Yoshi,
As Alper pointed out in the text from RFC3748, it is not optional to
produce an EMSK. Its usage is undefined at the moment, but, a compliant
implementation should be producing the EMSK, nevertheless. 

Regards,
Vidya

> -----Original Message-----
> From: Yoshihiro Ohba [mailto:yohba at tari.toshiba.com] 
> Sent: Thursday, November 16, 2006 10:31 AM
> To: Dondeti, Lakshminath
> Cc: Alper Yegin; hokeyp at opendiameter.org; emu at ietf.org
> Subject: Re: [Hokeyp] [Emu] Re: MSK but no EMSK
> 
> Hi Lakshminath,
> 
> RFC 3748 says:
> 
> "
>    Extended Master Session Key (EMSK)
>       Additional keying material derived between the EAP client and
>       server that is exported by the EAP method.  The EMSK is at least
>       64 octets in length.  The EMSK is not shared with the
>       authenticator or any other third party.  The EMSK is 
> reserved for
>       future uses that are not defined yet.
> "
> 
> Since EMSK usage is not defined yet, the use of EMSK is 
> virtually optional at this momement.  Since it was not 
> mandated in the beginning, it is not possible to change it 
> mandatory for a particular use in a future without loss of 
> interoperability with the existing deployment.
> 
> Am I missing something?
> 
> Yoshihiro Ohba
> 
> 
> On Thu, Nov 16, 2006 at 09:38:10AM -0800, Lakshminath Dondeti wrote:
> > At 06:27 AM 11/16/2006, Yoshihiro Ohba wrote:
> > >I made one comment around this in the HOKEY session.  The 
> intent of 
> > >my comment was that use of EMSK is optional.
> > 
> > Hi Yoshi,
> > 
> > Which document says that the "use" of EMSK is optional?
> > 
> > >There would be an
> > >interoperability issue if peer and server do not negotiate 
> on the use 
> > >of EMSK before actually using it.
> > 
> > The interoperability issue would only come up if there is 
> ambiguity or options.
> > 
> > Lakshminath
> > 
> > 
> > >Yoshihiro Ohba
> > >
> > >
> > >On Thu, Nov 16, 2006 at 11:01:15AM +0200, Alper Yegin wrote:
> > > >
> > > > I remember someone in Hokey WG meeting mentioned that not all 
> > > > methods generate EMSK (even though they generate MSK). 
> Is that accurate?
> > > >
> > > > Despite this RFC 3748 text?
> > > >
> > > >    In order to provide keying material for use in a
> > > >    subsequently negotiated ciphersuite, an EAP method 
> supporting key
> > > >    derivation MUST export a Master Session Key (MSK) of 
> at least 64
> > > >    octets, and an Extended Master Session Key (EMSK) of 
> at least 64
> > > >    octets.
> > > >
> > > > Alper
> > > >
> > > >
> > > > _______________________________________________
> > > > Hokeyp mailing list
> > > > Hokeyp at opendiameter.org
> > > > http://www.opendiameter.org/mailman/listinfo/hokeyp
> > > >
> > >
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> > 
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> > 
> 
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