Re: [Sip] Re: RLS and identity

Drage, Keith (Keith) wrote:

>Adam is also making generalisations when he states "inherently insecure P-Asserted-Identity mechanism". Noone has made any justification of this statement. I accept that P-Asserted-Identity has a restricted applicability, in that it needs a trust domain, and needs to fulfil a number of criteria, as listed by the template at the back of RFC 3325, but that does not make it insecure. Any mechanism is insecure if you do not follow the rules.
>  
>

I consider any network that has security properties of "crunchy security 
shell with soft, easily compromised filling" to be inherently insecure 
-- a single compromise anywhere in the system can be used to exploit the 
entire system; in 3GPP, this weakness can even be exploited across 
domains. Any network architecture with such a design guarantees that the 
security of any node in the system is no better than the security of the 
least secure node in the system. For sufficiently large systems, this 
degenerates to the same properties as little or no security, since the 
probability of at least one node being compromisable goes up 
geometrically with the number of nodes in the system [1].

Since P-Asserted-Identity works only in the framework of such systems, 
and relies exclusively on the crunchy shell for protection, I consider 
it inherently insecure.

/a

[1] For example, if you have a system with 2,000 nodes, each
    of which has a 99.9% chance of having been designed and
    configured to have appropriate security properties, there
    is still an 86.5% chance that at least one of those nodes
    will be exploitable, meaning that there is an 86.5% chance
    that the entire system can be exploited.
    (99.9% ^ 2000 = 13.5%)

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