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Re: BGP Security and PKI Hierarchies (was: Re: Wifi Security)

  • From: Steven M. Bellovin
  • Date: Tue Nov 22 15:55:32 2005

In message <17283.33635.774719.679@roam.psg.com>, Randy Bush writes:
>>>> I believe a web of trust can be operationally feasible only if the web
>>>> is more like a forest - if there are several well known examples of
>>>> "tops" to the web.  Otherwise, you have to be storing a plethora of
>>>> different signers' certificates to be able to validate all the
>>>> institution's certificates that come in.
>>>
>>> you need those certs to verify the live data anyway
>>> 
>> Right.  The real issue is the trust determination -- how do you know 
>> that the certificate corresponds to something resembling reality 
>> (whatever that is)?
>
>for how many years have i been asking you and your evil-minded cert
>designing friends for a pgp-like web of trust cert that could be
>used for just this application?
>

Actually, I don't do certs; it's my evil-minded friends...

That said, I think the problem is that we need an algebra of trust that 
will let a program, not a human, decide whether or not to trust a 
certficate.  You don't want to accept something if it's a twisty loop 
of subsidiaries or allied evil ASs vouching for each other.  OTOH, 
there are some situations where we know that absolute trust is 
indicated -- say, 701 signing 702's certificate, or an upstream signing 
the address certificate for a customer.  And it's not just honesty, 
it's competence you're assessing -- we've all seen problems when major 
ISPs didn't get their filters straight.

Furthermore, given that a trust algebra may yield a trust value, rather 
than a simple 0/1, is it reasonable to use that assessment as a BGP 
preference selector?  That would tie the security very deeply -- too 
deeply? -- into BGP's guts.

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb






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