eap Mailing List: Re: Comments on draft-ietf-eap-keying-08b.txt

[Jari Arkko (jari.arkko]

Hi Thomas,

Thank you for the comments. I mostly agree with them,
some notes inline:

> Three brief comments to 
> http://www.drizzle.com/~aboba/EAP/draft-ietf-eap-keying-08b.txt.
>
>
> 1) Some "independences" are capitalized, others not, e.g.
> 1.4.2 ... media independence 
> 1.4.3 ...  Media Independence ... 
>
> 2) It seems there is an inconsistency regarding what an EAP method exports.
> Figure 1 shows that an EAP method exports MSK,EMSK,IV, Peer-ID,Server-ID,
> Method-ID,Key-Lifetime.
>
> Section 2.2 now says 
> "In completion of EAP authentication, EAP methods on the peer and EAP
> server export the Master Session Key (MSK), Extended Master Session
> Key (EMSK), Initialization Vector (IV), Peer-ID, Server-ID, Session-ID and
> Key-Lifetime."
>
> I think 2.2 must be "Method-ID". 
> 3) Section 3.6. says, 
> "it is RECOMMENDED that EAP methods utilizing public key cryptography choose a
> public key that has a cryptographic strength meeting the symmetric key 
> strength"
>
> I'm not sure why you say "recommended" here? What else could one do?
>  
Its just an explanatory note that the claimed strength should
match the PK strength. I would not change anything here.

> RFC 3748 says: 
> "EAP methods supporting key derivation SHOULD be capable of generating an
> MSK and EMSK, each with an effective key strength of at least 128 bits."
>
> This implies that the effective key strength of public key cryptography must
> be (rougly) equivalent to that of symmetric key cryptography.
>
> In this context, the following statement of RFC 4017 appears wrong (at least 
> for me). Neither says RFC 3748, that an EAP method MUST derive a MSK and 
> EMSK, nor that the effective key strength MUST be 128 bit. 
>
> "Key strength.  An EAP method suitable for use with IEEE 802.11
>        MUST be capable of generating keying material with 128-bits of
>        effective key strength, as defined in [RFC3748], Section 7.2.1."
>  
RFC 4017 has a stronger requirement. I would have added
"at least" to the text of 4017 but its probably understandable
anyway...

--Jari