Re: [babel] WG adoption call for draft-do-babel-hmac (7/19 - 8/6)

[Markus Stenberg <[e-mail]>]

I have read the draft and support adoption.

That said..nit or two :-)

   Whenever B resets its PC, or whenever B doesn't know whether
   its PC has been reset, it picks an index that it has never used
   before (either by drawing it randomly or by using a reliable hardware
   clock) and starts sending PCs with that index.

I think there are 3 potential sources for index:

- nvram/flash (truly unique, frequently but not always available)
- magic timestamp (e.g. GPS, magical secure NTP might give us ~unique timestamp, or RTC that never goes backward for this purpose.. but typical routers do not have strictly monotonic hardware clocks the text notes)
- something pseudorandom that has sufficiently low collision likelihood given the number of bits of index

so I think the text (and some of the following) is slightly optimistic. I would probably just settle for a sufficiently low collision chance.

Also, I would like to have byte(/few bits) somewhere indicating the algorithm used for HMAC. Maybe I’m just tired and can’t see one that is already there.

Cheers,

-Markus