Subject: [eap] Re: Issue 210: No Name for "top EAP keying material"

From: Bernard Aboba <[email-masked]>
Date: Wed, 3 Mar 2004 20:13:08 -0800 (PST)

The text of Issue 210 is enclosed below.  One potential resolution to this
is to use the term "Long Term Secret" to refer to either a long-term
pre-shared key or a private key.  However, in RFC 2284bis we eliminated
discussion of the Master Key since not all methods use this, so I'm not
sure it makes sense to add references to this in the Key Framework
Document.

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Issue 210: No name for the "top EAP keying material"
Submitter name: Florent Bersani
Submitter email address: [email-masked]
Date first submitted: 12/16/2003
Reference:http://mail.frascone.com/pipermail/public/eap/2003-December/001997.html
Document:  KeyFrame-01
Comment type: E
Priority: 2
Section: 2.2
Rationale/Explanation of issue:

Although the EAP hierarchy is very clearly described in section 2.2, I
experienced some difficulties to present it to colleagues for a trivial
reason: the top EAP key (i.e. the one that is somehow involved in the MK
derivation e.g Ki in the EAP-SIM method, the private keys associated to
the digital certificates used within EAP-TLS) does not appear to have a
name. Things would become easier if there was standard terminology.

Requested change:

Add to section 2.2 at the beginning of the different key types
enumerations:

EAP Permanent Key (PK):
To perform authentication and key exchange, an EAP method uses a
permanent secret. This secret MAY belong either to the symmetric
cryptography or asymmetric cryptography category.

Add to Figure 2:
"(PK)" near the text "EAP method" in the top left corner of the figure
"(MK)" in the box labeled "EAP Method Key Derivation"

Add to Figure 3:
"PK," before "(MSK,TEKs)"

Add to Figure 4:
"PK," before "(MSK,TEKs)"

Add to appendix B:

"Pre-master secret": created or exchanged thanks to the PK which are
digital certificates in the case of TLS

[This wording "created or exchanged" wants to encompass all the TLS
possibilities: RSA, DH,...]

[In general, I don't like very much my wording but issue submitters have
to propose solutions to their issues, don't they ;-)?]
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From: Florent Bersani <[email-masked]>
Date: Thu, 04 Mar 2004 07:49:42 +0100

>sure it makes sense to add references to this in the Key Framework
I agree with you so why not "EAP (long term?) credential".

Wouldn't this wording allow for unambiguous naming of the root of the 
EAP key hierarchy Hierarchy and at the same time apply to the whole 
variety of methods' "root keys" (symmetric, asymmetric, OTP,...) - my 
quick answer, I'll go to the list to review the previous debates

So I suggest using the label "EAP long-term credential" and including 
text to explain that this credential might be instantiated in numerous ways:
"The EAP (long term) credential is the credential the peer and the 
server resort to when doing a full EAP authentication*. It might be a 
symmetric cryptography key, an asymmetric cryptography key, a one-time 
password generator,..."

My feeling was though that you only have (for now) essentially two types 
of credentials: symmetric and asymmetric ones.

Anyway, it is a minor issue but it in my opinion, naming the top of the 
tree would help to clarify things.

What do you think?

Florent

*I am still not happy with the wording since I feel "EAP full 
authentication" would have to be defined but my mentioning this here was 
that in fast reconnect schemes, you may not use the EAP (long term?) 
credential