At 2:29 PM -0700 6/14/02, Ed Gerck wrote:
>Stephen Kent wrote:
>
>> My examples of disjoint credential spaces in the physical world are
>> not unified and they ought not be. There usually is no incentive for
>> the issuers to cross certify in most cases for these separate roots,
>> and it creates new liability concerns, and raises trust issues.
>
>OTOH, it is a problem if you want to talk outside of your gopher hole ;-)
I anticipate belonging to a lot of communities (PKIs), just as I do today.
> >
>> Ed Gerck wrote:
>> The fundamental problem is that the PKI architecture cannot
>> >directly provide mutiple root functionality. You need to overlay bridge
>> >CAs and other artifacts in order to create the paths. Now, imagine a
>> >different mathematical structure, one that is not based on a hierarchy
>> >and yet works with hierarchical systems (as well as non-hierarchical
>> >systems liek a peer-to-peer network). Such structure could allow paths
>> >to be found, and validated, from one hierarchy (PKI, DNS) to another
>> >(PKI, DNS).
>>
>> I disagree; PKIs can accommodate multiple roots. Mesh certification
>> is and old concept (intrinsic in X.509), but it is way too complex
>> for most (if not all) folks to comprehend and manage. I always point
>> to the inability of people to program VCRs as an example of a lower
>> bound for people's tolerance of complexity. Mesh PKIs go way beyond
>> VCR programming.
>
>Certainly, as well as the explanation why "mesh certification" does not work.
>
>To begin, consider that a certified end-user key exists to establish assurance
>in the authenticty of the keying material; certification is the process for
>effecting such assurances.
right
>However, more generally, a certification chain can exist whose purpose
>is to 'distribute the (asymmetric) key". Key Distribution, unlike key
>certification, requires notions of revocation, compromise recovery, and
>management of risk to compensate for inadequate or costly procedures of
>key distribution..
I don't understand this. Because certs are signed, distribution is
relatively easy, e.g., I can store them and transmit them with
relative ease. I don't need to issue certs just to distribute keys.
Even for revocation this is true, if one uses CRLs.
>In such a simple theory, key certification validity is not a overly-variable
>quantity: the degree of variability is limited to the "legal fact"
>(affirmative
>fact exists, or does not exist) established when a using party ("relying
>party"?) *accepts* it, or not, as useful.
Oh, let's not bring legal issues into this. I don't consult my
general counsel about the length of passwords or the mandated
frequency of change, etc. when we're putting in place systems to
authenticate users. If we refrain from trying to make too much out of
a PKI, we ought to be able to do the same thing.
>The systemic purpose of key distribution is to provide a "metric space"
>whereby many procedures, which handle certification chain(s), may be
>(multiply) used to measure whether a given asymmetric key pertaining to
>an end-user is indeed useful, or not. The metric is an expression of
>relative certainity for a specific security problem, and application
>context, given all available knowlege of the operational vulnerablities.
I don't agree. I looked briefly at your reference (cited below) and
it begins by arguing about the difficulty of naming things uniquely
in the Internet. But in the DNS context, this is a solved problem, so
I don't think the extensive analysis you provide is applicable here.
>Try www.mcg.org.br/cie.htm , which uses such a geometric model for
>certification to show that PKI certification must depend on an external
>reference *even though* the external reference "cancels out" in the final
>result.
>
>> >Someone may add that the DNS is not really a hierarchy, it is just an
>> >ontology. My argument still holds for ontologies and also applies
>> >to how names are used in PKI certificates (as I have discussed
>> >elsewhere, see google). A certificate is just an authenticated assertion
> > >made within the context of a name space. The name space in a PKI
>> >forms an ontology and that ontology is defined by name space
>> >ownership, just like in the DNS.
>>
>> I don't know who would argue that the DNS is other than a singly
>> rooted tree,
>
>The DNS names do not have the same hierarchy that one associates
>per X.509/X.500 witth a DN. The DNS is less than a single rooted tree
>because there are no neccessarily hierarchical dependencies, just
>hierarchical placements.
Huh? Both DNS and X.500 use hierarchic names allocated in a
distributed fashion from a singly rooted tree. We have a convention
for how to map DNS names to DNs, using the DC attribute. I do not
understand the phrase "there are no neccessarily [sic] hierarchical
dependencies, just
hierarchical placements"
<snip>
Steve