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Re: Manual keying and replay prevention



>    Note that support for manual key distribution is required, but
>    its use is inconsistent with the anti-replay service, and thus a
>    compliant implementation must not negotiate this service in
>    conjunction with SAs that are manually keyed.
> 
> Why not?

The wording seems convoluted; as my impression was that manual keying
implies that no negotiation takes place.

I think the issue with manual keying and replay is recovery from a
reboot.. unless you store the receive-side replay state in stable
storage as each packet is processed, you can't allow the SA to survive
a crash without running the risk that you'll accept a replayed packet.

(On the send side, you could checkpoint every N packets, and waste up
to N packets of sequence space on a reboot.  if you tried a similar
hack on the receive side, you'd wind up needing to *ignore* up to N
incoming in-sequence un-replayed packets..)

Also, there's the issue of what to do when the replay counter maxes
out..

				- Bill


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