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Re: Comments on "Hybrid Auth. mode for IKE"
[cc: list trimmed...]
Pyda Srisuresh wrote:
<substantially trimmed...>
> > >> > 4. SA lifetime:
> > >> >
> > >> > The current metrics of "time-bound" and "Data-bound" for an
> > >> > SA lifetime do not seem adequate for remote access users.
> > >> > I would like to see a new metric like "network-connected-time"
> > >> > for SA lifetime. This new metric may be used in conjunction with
> > >> > other metrics (if the crypto algorithms mandate such a limiting
> > >> > criteria) or by itself.
> > >>
> > >> Why is not SA lifetime close enough to net sonnect time? Why is the latter
> > >> metric preferable?
> > >>
> > >
> > >How would you pick a close enough metric? Could be quite arbitrary.
> > >A user may have no way to know ahead of time, how long his/her sessions
> > >are going to have to be kept alive or how much data he/she is going
> > >to be exchanging. If these metrics are to be set infinitely large,
> > >then that defeats the purpose to start with.
> > >
> > >Most often than not, a user is likely to want to keep the negotiated
> > >security parameters unchanged throughout the connected time.
Then the user is risking compromise due to the dearth of ciphertext and
time the attacker is being given to attack the key with. Rekeying is a
minor expense which provides greatly increased security. The cost
associated with it is negligible, compared to the benefits.
If you insist on life-of-connection SAs, then configure your gateway so
that SAs have infinite lifetimes, and make it your policy that SAs are
dropped when connections are. I wouldn't do it, but you can...
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