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Unique MIDs
> Replaying an old Initiator-to-Responder message (#1) back to the
> Responder will result in the Responder sending an unexpected message #2
> back to the Initiator which will fail the hash check
If the responder allows the initiator to use non-unique message IDs then
this opens up a DoS avenue especially if PFS was used.
The RFCs make several references to unique IVs for the phase 2 exchanges
(i.e., unique MID). These references seemed to indicate unique IVs were
important for more reasons than just the case of having two simultaneous
Quick Modes taking place with the same message ID. The RFCs don't make any
statement about the temporal nature of the uniqueness. I assumed the
uniqueness of the MID/IV was constrained to the cookie. Even if there were
no cryptographic significance to mandating unique IVs there is still the
issue of DoS mentioned above.
-dave
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