Subject: [eap] EAP Key Management Framework (FYI)

From: [email-masked]
Date: Fri, 26 Aug 2005 14:31:42 +0200

In http://www.drizzle.com/~aboba/EAP/draft-ietf-eap-keying-08.txt,
we have

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+         ---+
   |                                                         |            ^
   |                EAP Method                               |            |
   |                                                         |            |
   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+   |            |
   | |                                 |   |             |   |            |
   | |       EAP Method Key            |<->| Long-Term   |   |            |
   | |         Derivation              |   | Credential  |   |            |
   | |                                 |   |             |   |            |
   | |                                 |   +-+-+-+-+-+-+-+   |  Local to  |
   | |                                 |                     |       EAP  |
   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                     |     Method |
   |   |             |               |                       |            |
   |   |             |               |                       |            |
   |   |             |               |                       |            |
   |   |             |               |                       |            |
   |   |             |               |                       |            |
   |   |           +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ |            |
   |   |           | TEK       | |MSK, EMSK  | |IV         | |            |
   |   |           |Derivation | |Derivation | |Derivation | |            |
   |   |           +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ |            |
   |   |                             |                 |     |            |
   |   |                 ^           |                 |     |            V
   +-+-|-+-+-+-+-+-+-+-+-|-+-+-+-+-+-|-+-+-+-+-+-+-+-+-|-+-+-+         ---+
       |                 |           |                 |                  ^
       | Peer-ID,        |           |                 |          Exported|
       | Server-ID,      | Channel   | MSK (64+B)      | IV (64B)    by   |
       | Method-ID,      | Bindings  | EMSK (64+B)     |             EAP  |
       | Key-Lifetime    | & Result  |                 |           Method |
       V                 V           V                 V                  V

        Figure 1:  EAP Parameter Import/Export

The non-public IV is derived from the secret keying material.

In NIST SP 800-56 however one find in section 5.8, Key Derivation Functions,
that "the output from a KDF shall only be used for secret keying material, 
such as a symmetric key used for data encryption or message integrity, [...]
Non-secret keying material (such as a non-secret initialization vector)
shal not be generated using the shared secret". 

I am not sure, shouldn`t the EAP key management better comply with NIST
recommendations?

/Thomas
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---

From: Jari Arkko <[email-masked]>
Date: Fri, 26 Aug 2005 15:38:25 +0300

>I am not sure, shouldn`t the EAP key management better comply with NIST
It would seem that this would only be a problem if
the IV were actually used somewhere in a public
manner.

Given that the use of the IV is already deprecated, I
wonder if we should take this depracation even further
and state that this value is reserved and must not be
used for any purpose.

--Jari