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RE: key change for TCP-MD5

  • From: Ross Callon
  • Date: Tue Jun 20 19:14:43 2006

At 12:12 PM 6/20/2006 -0700, Bora Akyol wrote:

The draft allows you to have a set of keys in your keychain and
the implementation tries all of them before declaring the segment
as invalid.
DoS against routers is of course a major concern. Using
encryption has the potential of making DoS worse, in the
sense that the amount of processing that a bogus packet
can cause is increased by the amount of processing
needed to check the authentication. If the router needs to
check multiple keys in the keychain before declaring the
segment as invalid, then this multiplies the effect of the
DOS by the number of keys that need to be checked.

No time synchronization required. No BGP message required.

The added cost for CPU-bound systems is that they have to try
(potentially) multiple keys before getting the **right** key
but in real life this can be easily mitigated by having a rating
system on the key based on the frequency of success.
This mitigates the effect of authenticating valid packets. However,
this does not appear to help at all in terms of minimizing the DOS
effect of an intentional DoS attack that uses authenticated packets
(with the processing time required to check the keys the intended
damage of the attack).


> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Iljitsch van Beijnum
> Sent: Monday, June 19, 2006 10:22 AM
> To: Randy Bush
> Cc: NANOG list
> Subject: Re: key change for TCP-MD5
> On 19-jun-2006, at 19:10, Randy Bush wrote:
> >>> try reading more carefully
> >> Didn't help...
> > how sad, as the whole document is about how to usefully be able to
> > introduce and roll to new keys without agreeing on a narrow time.
> Well, as you can tell from my message just now, I don't think
> going from agreeing on a narrow time to agreeing on a wider
> time is worth the trouble, especially since by adding a BGP
> message it would be possible to roll over if and as soon as
> both sides are ready, removing the "wait for some time and
> then see whether the other end really installed the new key"
> part from the proceedings.