Subject: [Pana] PaC-EP-Master-Key

From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 20 Dec 2005 01:39:40 -0500

In the current PANA spec:

"
   PaC-EP-Master-Key = HMAC-SHA-1 (AAA-Key, "PaC-EP master key" |
                                   Session ID | Key-ID | EP-Device-Id)
"

This means that the length of PaC-EP-Master-Key is 160-bit.

On the other hand, in draft-ietf-eap-keying-08.txt, a master key used
for deriving TSKs must be at least 64 octets in length and 160-bit
seems too short for PaC-EP-Master-Key.

I think a prf that can generate more octets should be used for
culculating PaC-EP-Master-Key, such as prf+ in IKEv2.

Regards,
Yoshihiro Ohba

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---

From: Rafa Marin Lopez <[email-masked]>
Date: Wed, 21 Dec 2005 20:09:15 -0500

Hi Yoshi

I agree with this. For example , in 802.11i that is the case. If PANA is
used to bootstrap PSK , PaC-EP-Master-Key cannot be used as is (PSK =
PaC-EP-Master-Key) becuase PSK is 256-bits.

Regards.

-- 
------------------------------------------------------
Rafael Marin Lopez
Faculty of Computer Science-University of Murcia
30071 Murcia - Spain
Telf: +34968367645    e-mail: [email-masked]
------------------------------------------------------

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From: Yoshihiro Ohba <[email-masked]>
Date: Thu, 29 Dec 2005 14:45:15 -0500

(I associated this issue with old Issue 169 on PANA lower layer
ciphering, http://danforsberg.info:8080/pana-issues/issue169)

OK.

Here is my suggested change:

Change:

"
   The PaC-EP-Master-Key derivation algorithm is defined as follows.

   EP-Device-Id is the Data field of the Device-Id AVP for the
   corresponding EP.
"

to:

"
   The PaC-EP-Master-Key derivation algorithm is defined as follows.

   PaC-EP-Master-Key = The first 64 octets of 
                       HMAC-SHA1+(AAA-Key, "PaC-EP master key" |
                                  Session ID | Key-ID | EP-Device-Id)

   HMAC-SHA1+ is an instance of prf+ function defined in IKEv2
   [RFC4306], where the instance uses HMAC-SHA1 as the prf
   (pseudo-random function).

   EP-Device-Id is the Data field of the Device-Id AVP for the
   corresponding EP.
"

(Also, all other references to IKEv2 will be updated to point to
RFC4306).

Yoshihiro Ohba