At our recent ITU-T SG17 meeting in Geneva we discussed and rejected
Defect Report 320
(http://www.x500standard.com/uploads/Defects/DR_320.pdf) from AFNOR.
This DR advanced an argument that Distinguished Names may not be unique
and as such, the DN of the Certificate User may not be unique.
The directory group believes that Distinguished Name values must be
unique and unambiguously identify a single entity, hence the use of the
The DR states â€œthe DN of the issuer name cannot be guaranteed to be
uniqueâ€?. X.509 takes its definition of DN from X.501. Clause 9.2 of
X.501 specifies the definition of DistinguishedName. This clause
states A name shall be unambiguous, that is, denotes just one object.
Clause 9 goes on to state: It is the responsibility of the relevant
naming authority for an entry to ensure that this is so by
appropriately assigning distinguished attribute values. Allocation of
RDNs is considered an administrative undertaking that may or may not
require some negotiation between involved organizations or
administrations. This Directory Specification does not provide such a
negotiation mechanism, and makes no assumption as to how it is
The standard takes an axiomatic view of the concept that a
distinguished name unambiguously identifies a single entity. Things
break if two entities identify themselves using the same name. We
don't let two entities have the same domain name or the same email
address. Why? - because things wouldn't work.
The directory group does not accept the DRâ€™s basic argument. We
believe that if two entities present the same name and a CA issues a
certificate to each, that CA made a mistake - not a naming authority
mistake, since a CA is not an naming authority (although one entity can
be both), but an entity to key binding mistake that leads to confusion
and even worse, a security risk.
We believe that if two entities claim the same name as top level CAs,
there is a political/procedural breakdown much like the domain
ownership arguments we have seen. No one argues that the Internet
protocols should be modified to solve that problem. The conflict is
resolved and one entity is assigned the name. The group believes that
this is the only reasonable solution for Distinguished Naming. One
votes for the CA of choice by configuring it as an anchor.
One of the participants in the directory meeting stated that
Certification Authorities are being deployed with names not acquired
from naming authorities but with names arbitrarily chosen assuming that
no other CA is or will be operating under that name. That participant
further stated that the IETF provides no guidelines on ensuring that
the names of CAs are unambiguous.
The directory group requests the IETF PKIX group to comment on this
statement. If the statement is correct, we ask the IETF to consider
putting a mechanism in place to prevent conflict, e.g. a list of
existing CA names that deployers of new CAs could check for naming