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Gee, shared secrets suck (was: Re: SOI: identity protection and DOS)

  > in addition to that: if you backup the configuration of your IPsec enabled
 > device and you are using shared secrets you must ensure that nowbody has a
 > chance to read the backup. if you are using public keys that are
 > authenticated using preshared information you must only make sure that the
 > backup is tamperproof or perhaps even tamper evidence is sufficient.

Why is that?  Is it because you have somehow forgotten to also backup
the private key part of the public/private key pair?   Sure, as long as
you don't store the private key anywhere in your backups, then you don't
have to worry about it being stolen/lost/compromised---whether it's what
we think of as a 'pre-shared secret' or 'uncertified private/public key pair.'


But none of this matters.  No one is arguing why authentication methods
using public keys or digital certificates are better for authentication
and security than pre-shared secrets.   

The fact is, however, that end users of these products have
overwhelmingly voted with their implementations to use pre-shared
secrets for site-to-site authentication (and, if you consider SecurID as
a 'preshared secret,' also for remote access).  Creators of these
products have done an abyssmal job of enabling either interoperability,
security, and manageability using anything longer than an easily
rattled-off string.  

If you want to be sure that no one uses IKEv2 in real networks, then
force them to transfer a 1024-bit (or longer) value, or even the 128-bit
hash of that value.  

Everyone agrees that PSS have defects compared to other authentication
methods.  You protocol geeks have to pull your heads out of the packets
and look at how people have actually implemented the protocol management
system and how end users have actually implemented VPNs.  You must have
something akin to the simplicity and shortness of PSS to ensure that
people will be able to at least prototype these systems in their
networks.  

When they go the long haul and build huge VPNs---if they ever choose to
do that---then other authentication methods, such as digital
certificates, will be welcome additions to the protocol.  But every
large VPN installation starts out as a small VPN installation, and 99%
of small VPN installations start with pre-shared secrets.

jms

--
Joel M Snyder, 1404 East Lind Road, Tucson, AZ, 85719
+1 520 324 0494 x101 (voice)    +1 520 324 0495 (FAX)
jms@Opus1.COM    http://www.opus1.com/jms    Opus One
Electronic mail is always the best way to contact me.
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