Re: SOI: preshared

[Henry Spencer <[e-mail]>]

On Mon, 19 Nov 2001, Michael Thomas wrote:
> 1) Should we deem peer-peer preshared keying bogus?

I think the crucial requirement here is for some *simple* method of
authentication, which can work effectively without outside assistance or
elaborate supporting infrastructure, as a fallback measure for use in
simple or constrained situations and in troubleshooting.  As a historical
analogy, consider hosts.txt (aka /etc/hosts) vs. DNS. 

The simple mechanism doesn't have to scale, and it doesn't have to be
particularly convenient to administer, but it should be there.

There is no strong reason why the simple mechanism can't be public-key
signatures rather than shared secrets.  Public keys are immensely superior
to shared secrets in most ways, and as we've demonstrated with FreeS/WAN,
they don't have to be much more complicated to use.  (There's a widespread
myth that you can't do public keys without certificates; not so.)

Anything involving a PKI definitely does not qualify.

> 2) If not, should SOI inherently be a dual (triple...)
>    authentication mechanism protocol?
> 3) If so, how do we bound the authentication
>    mechanisms to keep IKE manageable?

There needs to be an easy-to-administer highly-scalable mechanism for
large-scale use, and a dead-simple zero-infrastructure mechanism for
experimenting, constrained situations, and troubleshooting.  If those
mechanisms can't be the same at the keying-protocol level -- we think they
can, by the way -- then that's two.  There is no requirement for more. 

                                                          Henry Spencer
                                                       [e-mail]