Re: Bellovin's and Ahar's attacks

[Danny.Nessett@eng.sun.com (Dan Nessett)]

>  
>  A lot depends on our assumptions.  For TCP, it's probably feasible, so
>  long as rekeying occurs more frequently than the TIMEWAIT period.  For
>  UDP, there's no mandatory dead time in the protocol.  I strongly suspect
>  that we absolutely must use very rapid key changes, though -- per user
>  (though with AH+ESP for some services), per packet (a la SKIP), or per
>  socket.  Nothing less seems to guard adequately against both replay attacks
>  and the CBC cut-and-paste attack that I outlined.
>  

I agree that rapid rekeying is a good idea. However, it isn't sufficient for
all cases.

By the way, the replay attack Ashar suggests relies on the ability of an
intruder running on a machine discovering which port to use to receive the
replayed traffic. Since ESP hides this information in the encrypted
part, the intruder must use indirect methods to discover this.

Dan

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