Re: [6tisch] TSCH and CCM security proofs

[Michael Richardson <[e-mail]>]

Tero Kivinen <[e-mail]> wrote:
    > Michael Richardson writes:
    >> > Implementations MUST use different L2 keys when using different MIC
    >> > lengths, as using same key with different MIC lengths might be
    >> unsafe > (i.e., using same key for both MIC-32 and MIC-64). See IEEE
    >> 802.15.4 > Annex B.4.3 for more information.
    >> 
    >> This seems like it isn't a problem.  It would apply to network-wide
    >> keying only.

    > It applies all keys, not only network-wide keys.

yes, but if one uses 802.15.9, then the likelyhood of repeated keys is pretty
low, right?

    >> While I guess we could include multiple Link_Layer_Key with the same
    >> key_id, and a different key_usage, that wasn't the intention.  I guess
    >> one could use a different K1 and K2 with a different MIC length, but
    >> have no idea why a network would want to mix MIC-32 and MIC-64.

    > Most common use might be someone using MIC-32 for beacons, but using
    > MIC-64 for actual data or something like that.

Yes, but why do that?
What's the benefit?

    > draft-ietf-6tisch-minimal-security seems to be using different keys
    > when the mic length is different (k1, and k2), and when k1 and k2 are
    > same it will always use same mic length, so there is no problem there.

    > Anyways it might good idea to add the warning somewhere, just incase
    > someone adds new combinations without realizing this problem.

okay.


-- 
Michael Richardson <[e-mail]>, Sandelman Software Works
 -= IPv6 IoT consulting =-