Paul Hoffman;
Until PKIs are able to represent the rich diversity of trust
relationships that exist in the real world, they are mere curiosities
with marginal practical value.
PKIs are able to represent the blah blah blah; your software isn't yet
translating that into something that you want to use.
It is not a software issue.
That you can construct a PK structure to represent a set of trust
relationships for some purpose does not mean that there is some
general purpose PKI.
There isn't.
That is, that you must construct a PK structure for every different
purpose is not a software issue but an operational problem too complex
and costly to be solvable.
Masataka Ohta
PK
Shared key cryptography with KDC, either, does not offer the general
purpose infrastructure, though shared key structures are easier to
maintain.