While we are on the subject of what things mean, I have been having some
discussions with RSA regarding their Commercial Hierarchy CA.
In this case, the issue is "What does a X.509 Certificate mean or imply",
and likewise what is implied by a digital signature that is authenticated by
said certificate. I claim that an X.509 Certificate in and of itself means or
implies almost nothing. In particular, even if (especially if) the issuing CA
is a corporation, all that is being claimed or vouched for by that CA is
the fact that the Distinguished Name contained is globally unique. The
_hope_ is that there exists a unique person whose given name corresponds
to that DN, and that he or she as at least something to do with that CA--
maybe addressability, at least.
The _presumption_ is that there is some degree of"affiliation", but this
could include employment (full or part-time), being a spouse or dependent
of an employee, a contractor or vendor, an authorized visitor, a building
tenant, etc., etc. Unfortunately, there is no convenient way to define
the degree of affiliation within the certificate itself, except by the rather
ugly hack of using something like Organizational Unit Address=Employee,
or OUA=Non Resident Visitor. (I suspect, but haven't confirmed, that the
standards groups and the NADF might frown on such a usage.)
Clearly (to me at least), if the X.509 certificate can't define what the
affiliation
is between the CA and the DN in the certificate, it is difficult to establish a
consistant policy as to what type of identification dcouments must be
presented to verify that affiliation. If I claim my daughter as a dependent,
is the CA obligated to insist on my proving that I furnish more than half of
her support?
If the degree of affiliation is not clearly established, then what liability,
if any,
does the company or the CA have for acts committed by me that might obligate
the company? Or better yet, what liability do either I or the company have if
someone steals my key and forges my signature to some arbitrary document?
I'm taking the position with RSA that an X.509 certificate implies absolutely
nothing,
ESPECIALLY and SPECIFICALLY with respect to any liability, unless and until
some other document is signed by both the user and the organization that is
empowering him to do something.
The real question is how to balance the computer and physical security
requirements
for my private key and the private key of the CA, versus the risks and
liabilities
associated with someone stealing my key and using it to forge my name to an
apparent obligation.
If there isn't any way to specify the various caveats and limitations of
liability in
the certificate itself, then I claim that we have to take the position that my
digital signature means or implies NOTHING AT ALL, unless I agree that it does
mean
something in document that is siimilar to my Affidavit of Legal Mark, or else a
bilateral
or multilateral agreement similar to an EDI Trading Partner Agreement, wherein
I
agree to honor and be bound by my digital signature as though it were my
written
signature, but only within the caveats and limitations that I have agreed to.
Obviously I can place various disclaimers within any text that I might write
that
would limit my obligations appropriately, including whether I even agree with
the signed
text, but I can't assume that my opponent will be as punctilious when signing
my name!
Therefore, if a signature means anything at all "in vacuuo" with respect to a
given
piece of text, and I have no way of predefining the conditions under which it
applies,
then my liabilities are unbounded, and there is no way of protecting my keys
adequately
to be worth that risk. I can't even risk having authorship implied by my
signature, because
I might be liable for libel or slander. (It really isn't Bob Jueneman who
writes all this stuff,
but rather someone who is impersonating him. The real Bob Jueneman is much
smarter, and
not nearly so long winded! :)
Arguments, violent agreements, etc.?
Bob(?)