BPM Mixmaster Remailer wrote:
> By using this generic term "PKI" the authors leave a great deal of
> confusion about which systems they are criticizing. Some of their
> "risks", such as the one quoted above, would apply to all of these
> PKIs, including SPKI. Others are more specific to current X.509 based
> hierarchical certification systems. Some don't address the PKI at all,
> but worry about things like user interfaces, criticisms that can be
> directed at virtually any form of security software.
Slightly tangentially, but worth observing, I think: current X.509 based
PKI is only nominally hierarchical. That is, X.509 would _like_ the DN
to be allocated hierarchically, but in practice this does not happen.
Each CA has its own namespace, there is no-one above CAs in the
hierarchy, and only one layer below (the entity for whom the CA provides
a certificate). This is pretty flat for a "heirarchy" by anyone's
reckoning.
SPKI's main beefs with X.509 (AFAIK) are that:
a) X.509 tends to want to be identity-based, which is a poorly defined
concept at best (SPKI leans towards roles or capabilities)
b) X.509 is based on a lot of difficult-to-get-right stuff that just
gets in the way of the real meat: signing public keys and attaching some
attributes to them. The fact that every X.509 package of any breadth is
peppered with exceptions to cater for every other package's cockups is
definitely evidence is SPKI's favour, IMO.
The downside of SPKI, of course, is the usual one that seems to dog good
ideas: no-one uses it.
Cheers,
Ben.
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