eap Mailing List: issue: counter length (review of eap-keying-08 by mats naslund)

[Jari Arkko (jari.arkko]

Submitter name: Mats Naslund
Submitter email address: Mats.Naslund [at] ericsson.com
Reference: (this email)
Document: Keying Framework
Comment type: T
Priority: 1
Section: multiple
Rationale/Explanation of issue:

Lower Layer
    The lower layer Secure Association Protocol MUST generate a fresh
    session key for each session, even if the keying material and
    parameters provided by EAP methods are cached, or the peer or
    authenticator lacks a high entropy random number generator.  A
    RECOMMENDED method is for the peer and authenticator to each
    provide a nonce or counter of at least 128 bits, used in session
    key derivation.

MN: If it is a counter, I don't see why it needs to be 128 bits...
Only a few bits will change anyway each time a new key is generated.