Re: [pkix] Self-issued certificates

Erwann Abalea <> Mon, 13 July 2015 01:52 UTC

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Date: Mon, 13 Jul 2015 03:52:16 +0200
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From: Erwann Abalea <>
To: Peter Bowen <>, "<>" <>
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Subject: Re: [pkix] Self-issued certificates
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Bonsoir Peter,

This isn't a self-issued certificate in X.509/RFC5280. It's a subordinate
CA. Section 6.1 clearly defines how one knows if issuer and subject are the
same entity.

Entities in X.509 are purely technical; your company named "Example Trust
Services" doesn't exist in this standard. If it existed, there should be a
way to express if it's the same entity when it's located in the US or in MY
(think about Digicert's certificates).

You're "free" to change the rule behind section 6.1 to match your idea of
what an entity is, for your own set of applications, but it will be
incompatible with the rest of the world. This has been done with electronic
passports (BAC), where an entity is defined by the countryCode alone when
validating CRLs, and the complete DN when validating a certificate chain.

Le lundi 13 juillet 2015, Peter Bowen <> a écrit :

> I'm trying to make sense of the definition of "self-issued
> certificates" in RFC 5280 (and X.509)
> Section 3.2 provides a definition: "Self-issued certificates are CA
> certificates in which the issuer and subject are the same entity."
> However section 6.1 says "A certificate is self-issued if the same DN
> appears in the subject and issuer fields."
> While it is clear that all certificates with the same DN for subject
> and issue are self-issued, it is unclear to me whether a certificate
> with different DNs could be self-issued.  Section 6.1 could be giving
> one example of how a certificate could be self-issued or section 6.1
> could be a limiting definition.
> Consider the following example:
> Example Trust Services has two different private keys.  Each key has a
> single associated DN:
> Key0 has DN O=Example Trust Services, OU=Global Trust Anchor
> Key1 has DN O=Example Trust Services, OU=Commercial Trust Anchor
> There is a CA certificate created with
> Subject: O=Example Trust Services, OU=Commercial Trust Anchor
> Subject Public Key: Key1
> Issuer: O=Example Trust Services, OU=Global Trust Anchor
> Signed by Key0
> Is this CA certificate considered a self-issued certificate?
> Thanks,
> Peter