Re: [Emu] Agenda Take 2

["Joseph Salowey (jsalowey)" <[e-mail]>]

Hi Dan,

Could you describe the technical differences between the approach in
draft-harkins-emu-eap-pwd-00.txt and existing approaches of SRP, SPEKE
and EKE?  

Thanks,

Joe 

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On 
> Behalf Of Dan Harkins
> Sent: Sunday, March 02, 2008 11:07 PM
> To: SeongHan Shin
> Cc: 'Kazukuni Kobara'; [e-mail]
> Subject: Re: [Emu] Agenda Take 2
> 
> 
>   Hi Shin,
> 
>   I'll put this on the list for cleanup in the -02 version.
> In section 2.6.3.2 it describes constructing the password 
> element for a prime modulus group. It says:
> 
>       pwd-value = KDF(pwd-seed, "EAP-pwd Affixing the PWE", len(p))
> 
>       PWE = pwd-value mod p
> 
> this should be:
> 
>       pwd-value = pwd-value mod p
> 
> We want to ensure the value stretched to the length of the 
> prime is numerically less than the prime. Section 2.6.3.2 
> goes on to say:
> 
>    The PWE is then computed by exponentiating the pwd-value 
> to the value
>    ((p-1)/r) modulus the prime.
> 
>       PWD = pwd-value ^ ((p-1)/r) mod p
> 
> I'm not sure where PWD came from :-). The convention is 
> capitals for elliptic curve groups to distinguish between 
> elements and scalars. There is no such convention for prime 
> modulus groups so it should be:
> 
>    The pwe is then computed by exponentiating the pwd-value 
> to the value
>    ((p-1)/r) modulus the prime.
> 
>       pwe = pwd-value ^ ((p-1)/r) mod p
> 
> And then that "pwe" is used in 2.6.4.2. The idea is we take a 
> pwe-seed derived from the secret and identities and stretch 
> that using the KDF into a pwd-value which we reduce modulo 
> the prime. The pwd-value is then used to construct the 
> password element, pwe, by exponentiating as described above-- 
> pwd-value ^ ((p-1)/r) mod p. I obviously messed up the 
> description of that.
> 
>   As I said, I'll clean this up in the next version. If you 
> do find any security issues with this draft please let me 
> know. And also if there are other typographical errors or 
> similar issues you come across please tell me so I can clean them up.
> 
>   regards,
> 
>   Dan.
> 
> On Sun, March 2, 2008 10:27 pm, SeongHan Shin wrote:
> > Dear Dan Harkins,
> >
> > Sorry, I didn't know that the ID is updated.
> > Anyway, I'll go through the new ID.
> >
> > By the way, is "pwe" in section 2.6.4.2 the same as "PWE"?
> >
> > Best regards,
> > Shin
> >
> > -----Original Message-----
> > From: Dan Harkins [mailto:[e-mail]]
> > Sent: Monday, March 03, 2008 2:17 PM
> > To: SeongHan Shin
> > Cc: [e-mail]; 'Kazukuni Kobara'
> > Subject: Re: [Emu] Agenda Take 2
> >
> >
> >   Hi Shin,
> >
> >   That draft has been updated. Please see the -01 version. 
> That is the 
> > one that will be presented in Philly and is, I believe, 
> resistant to 
> > off-line dictionary attack. If you know of an attack against it I 
> > would be extremely interested in hearing about it.
> >
> >   regards,
> >
> >   Dan.
> >
> > On Sun, March 2, 2008 7:16 pm, SeongHan Shin wrote:
> >> Dear all,
> >>
> >> This is Shin.
> >> I read the below ID (Password only Mechanism) 
> >> http://tools.ietf.org/id/draft-harkins-emu-eap-pwd-00.txt
> >> to be presented at IETF 71.
> >>
> >> The idea of the protocol seems interesting.
> >> However, I found that the protocol is susceptible to off-line 
> >> dictionary attack.
> >> If someone is interested, I'll show how the attack works.
> >> (you may already know that.)
> >>
> >> Best regards,
> >> Shin
> >>
> >>
> >> -----Original Message-----
> >> From: [e-mail] [mailto:[e-mail]] 
> On Behalf Of 
> >> Joseph Salowey (jsalowey)
> >> Sent: Thursday, February 28, 2008 8:04 AM
> >> To: [e-mail]
> >> Subject: [Emu] Agenda Take 2
> >>
> >> EMU Agenda
> >> IETF 71
> >> THURSDAY, March 13, 2008
> >> 0900-1130 Morning Session I
> >> ---------------------------------------------
> >> + Administrivia (5 min)
> >>  - agenda, blue sheets, note takers
> >>
> >> + Document Status (5 min)
> >>  - EAP-TLS  - draft-simon-emu-rfc2716bis-13.txt
> >>  - EAP-GPSK - draft-ietf-emu-eap-gpsk-08.txt
> >>
> >> + Charter Revision Status (70 min)
> >>  - General text (10 min)
> >>  - Tunnel Method (20 min)
> >>  - Secure Password Only Method (20 min)
> >>  - Channel Bindings (20 min)
> >>
> >> + Tunnel Method Requirements (30 min)
> >>  - draft-salowey-emu-eaptunnel-req-00.txt
> >>
> >> + Channel Bindings (20 min)
> >>  - draft-clancy-emu-chbind-00.txt
> >>  - draft-clancy-emu-aaapay-00.txt
> >>
> >> + Password only Mechanism (20 min)
> >>  - draft-harkins-emu-eap-pwd-00.txt
> >> _______________________________________________
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> >>
> >>
> >>
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> >>
> >
> >
> >
> >
> >
> >
> 
> 
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