Erik and Kyle,
Erik, you said:
" I am completely aware that X.509 has a life
outside directory, (...)
as to distinguished name, it seems too late to change
It is never too late.
X.509 does not define what a DN is.
ITU-T Rec. X.501 (11/2008), alias ISO/IEC
9594-2:2008, defines it only in the context of a DIT
9.1.3 distinguished name (of an entry):
Every object entry, alias entry, and subentry has at least one distinguished
If any RDN for the entry or any superior entry includes an attribute for
which there exist multiple distinguished
values differentiated by context (as
described in 9.3), then the entry shall have multiple distinguished names
differentiated by context. The primary distinguished name is that
distinguished name in which each RDN has the
primary distinguished value of each
contributing attribute as the main value in the RDN construct.
Furthermore, X.509 includes inappropriate
"Although the CAs are unambiguously
defined by a distinguished name in the DIT, .."
It is the time to allow the existence
of X.509 without using a Directory.
Kyle, you said: :
"Unfortunately, the original designers appear
to have not thought about what
would happen if you had a DN collision with multiple certificates and keys".
I would rather say: "The original designers
appear to have not given sufficient information about what
would happen if you had a DN collision".
The reality as that a DN name is only
unique for the CA which has issued it.
This statement is valid for the next upper the CA, and until a root CA
This means that only the sequence of
DN is unique for a given trust anchor.
In order to avoid any name collision
when DN are used for access control purposes, in the most general case
the structure of name placed in an ACL should start with a trust anchor
and be followed by a sequence of DNs.
When there is a single trust anchor,
the first element may be omitted,
... but only as long as there is not a second trust anchor later on.
When there is a single certification
path under that single trust anchor, the intermediate DNs of the CAs may
... but only as long as there is not a second certification path below
that trust anchor.
This guidance is not given anywhere.
This is an important discussion.
I am completely aware that X.509 has a life outside directory, although
directories, especially LDAP systems, are often used for holding the
different PKI components. In my effort to modernize X.509, I am trying
remove references to directory where it is not necessary. The main directory
content is the schema information (attribute types, object classes and
matching rules) for holding and accessing PKI/PMI components.
As to distinguished name, it seems too late to change that. It is part
many profiles and also of RFC 5280.
I do not believe that it would be wise to separate the content of X.509
two different documents. X.509 is well established and well known. Putting
the non-directory stuff into a separate document will cause confusion and
many references will have to changed.
(ASN.1 was never part of X.500, but of X.400 (1984), and it was separated
Mobile: +45 2097 1490
e-amail: era <at> x500.eu
Fra: Kyle Hamilton [mailto:aerowolf <at> gmail.com
Sendt: 1. december 2011 03:43
Til: Tom Gindin
Cc: Erik Andersen; PKIX
Emne: Re: [pkix] Unclear public-key certificate definition in X.509
On Fri, Nov 12, 2010 at 4:38 PM, Tom Gindin <tgindin <at> us.ibm.com>
> It no longer has the problem which it had
before. Of course, it's
> a little odd to describe a certificate as a function of specifically
> DN of the issuer, since the critical functional dependency is on the
> issuer's key pair.
The original X.509 use-case was that the Directory was everything, that
everything could be Distinguishably Named, and that the Distinguished Name
was the correct indexing system. The problem is that the original
hadn't had the experience of a decade of nearly universal worldwide
deployment, with the format being extended into realms it was never intended
Perhaps X.509 could be formally decoupled from X.500, or (much like ASN.1)
the data format and semantics could be moved to a different standard while
the DIT bindings remain in X.509.
> The CA(A) expression just confuses me, because it suggests that the
> a function of the subject name.
Unfortunately, the original designers appear to have not thought about
would happen if you had a DN collision with multiple certificates and keys.
The key to the lock is unique, which means that it also meets the
requirement to be a database key. The key is the key; the binding
the rest is just metadata.