Subject: [eap] Issue on eap-keying: PMK naming

From: Florent Bersani <[email-masked]>
Date: Mon, 04 Oct 2004 15:32:55 +0200

Description of issue: possible confusion between PMK naming and PMKID

    Submitter name: Florent Bersani

    Submitter email address: [email-masked]

    Date first submitted: 10/04/2004

    Document: Keying Framework

    Comment type: 'E'ditorial

    Priority: '1' Should fix

    Section: 2.4 and 3.4.1

    Rationale/Explanation of issue:

I find the following confusing. In section 2.4, I read

"PMK Name

       The PMK has no name of its own, and is only identified by the AAA-
       Key from which it is derived."

but in Section 3.4.1, I find "PMKID (security association 
identifier)"... so it seems to me that the PMK has no name but has an 
identifier (defined in clause 8.5.1.2 of IEEE 802.11i IIRC). I guess it 
could be worth clarifying this subtlety, wouldn't it?

Requested change

Would our 802.11i experts approve the following:
"PMK Name

       The PMK may be named by its identifier PMKID defined in clause 
8.5.1.2 of [IEEE80211i]."

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From: Jari Arkko <[email-masked]>
Date: Tue, 05 Oct 2004 00:13:35 +0300

> 8.5.1.2 of [IEEE80211i]."

I agree that the current text is confusing. On the other hand,
there's a distinction between what the keying framework documents
and what additional things may be done by link layers. Here's
a slightly modified text suggestion:

   PMK Name

     This document does not specify any naming scheme for the PMK.
     The PMK is only identified by the AAA-Key from which it is
     derived.

     Note: IEEE 802.11i names the PMKID for the purposes
     of being able to refer to it in the Secure Association
     protocol; this naming is based on a hash of the PMK itself
     as well as some other parameters (see Section 8.5.1.2 [ref]).

--Jari

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From: Florent Bersani <[email-masked]>
Date: Tue, 05 Oct 2004 08:52:15 +0200

Jari Arkko wrote:

>> identifier (defined in clause 8.5.1.2 of IEEE 802.11i IIRC). I guess 
>> it could be worth clarifying this subtlety, wouldn't it?
>>
>> Requested change
>>
> and what additional things may be done by link layers.

OK  but my understanding is that the PMK is bound to a specific link 
layer, namely IEEE 802.11i

(see e.g. section 2.1: "Pairwise Master Key (PMK)
     The AAA-Key is divided into two halves, the "Peer to Authenticator
     Encryption Key" (Enc-RECV-Key) and "Authenticator to Peer
     Encryption Key" (Enc-SEND-Key) (reception is defined from the point
     of view of the authenticator).  Within [IEEE80211i] Octets 0-31 of
     the AAA-Key (Enc-RECV-Key) are known as the Pairwise Master Key
     (PMK).  In [IEEE80211i] the TKIP and AES CCMP ciphersuites derive
     their Transient Session Keys (TSKs) solely from the PMK, whereas
     the WEP ciphersuite as noted in [RFC3580], derives its TSKs from
     both halves of the AAA-Key.")

> Here's

I guess I understand that the "names" that eap-keying defines are the 
ones to be included in the document, hence, since it is 802.11i which 
defines the PMK "name", this name has not its place in the document.

Perhaps sth like what's writtent about the TEKs, i.e., "the PMK naming 
is specified in IEEE 802.11i" would do just fine but the text jari 
proposes is OK for me,  although I am not sure what "naming the PMKID 
means". Wouldn't "IEEE 802.11i names the PMK thanks to a PMKID..." be 
better?

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From: Jari Arkko <[email-masked]>
Date: Tue, 05 Oct 2004 14:21:45 +0300

Hi Florent,

> layer, namely IEEE 802.11i

Hmm... yes, indeed. Thinking about this again, your text
starts to sound better.

--Jari