Re: [ipcdn] FW: DISCUSS: draft-ietf-ipcdn-bpiplus-mib-14

That address most of my concerns.  But I also said this:

  The Security Considerations section says

      The time to crack DES could be additionally
      mitigated by a compromised value for the TEK lifetime and Grace Time
      (up to a minimum of 30 minutes for the TEK lifetime, see
      Appendix A [1]).

  That's only partially correct.  These keys are confidentiality keys; 
  they're still valuable even after they're no longer in active use, 
  because they can be used to decrypt old traffic.  (By contrast, old 
  authentication keys are useless to an attacker.)

You need to strengthen your text; while frequent key changes help,
an attacker can often select what to attack.  For example, email checking
is generally timer-driven; someone monitoring the link can easily spot
an eamil session by noticing the periodicity.  For example, in the middle
of the night, when there's little email traffic (except, of course, for
the daily spam load), there will be a set of very similar (in length
and timing) packets in each direction, every N minutes, where N is probably
in the range 5-15 minutes.  Select the confidentiality key for this
period, attack it, and recover the user's email password.  For that
attack, a key lifetime of 30 minutes or 30 days is the same -- it's a
targeted attack.

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