+1 to what Bob sez.

Emphasis on the “I” in PKIX. It’s not like we’re creating an alternative 
infrastructure here.

LL


> On Oct 10, 2025, at 11:09 AM, Robert Moskowitz 
> <[email protected]> wrote:
> 
> Fun stuff.
> 
> Hannes is right that the 'X" is from X.509.  Also right that PKIX refers to 
> the whole infrastructure.
> 
> So the former implies these are NOT PKIX.  But the later, in the natural 
> evolution of language (I have been having a lot of these discussions with my 
> wife, she really deplores the dilution of "awesome"), is that PKIX includes 
> all standardized reencodings of X.509 data envelopes. 
> 
> I mean we COULD use PKIXC:  Public Key Infrastructure using X.509 reencoded 
> in CBOR.  
> 
> But that borders on ridiculous.  Plus it is a marketing thing.   Make it 
> complex enough and watch people leave the room.
> 
> More fun is the draft defines a field NOT in X.509.  That is the signature 
> over the CBOR object in place of the CBOR encoding of the signature over the 
> ASN.1 object!
> 
> Let's just confuse the bejeepers out of people here. (and those poor AI 
> systems)
> 
> Languages evolve.  Lots and lots of years ago I got REALLY upset over the 
> verb "ecologize".  Note I have a degree in Botany, in Secessional Ecology, 
> along with my degree in Computer Science.  And back then in the early '70s, 
> ecology was NOT a commonly known area of science.  One of the profs in 
> linguistics told me to get a life; language does! 
> 
> So C509 is within the scope of PKIX.  No need to add to the alphabet soup 
> over this.
> 
> My 2c worth on this.
> 
> Bob
> 
> 
> 
> On 10/10/25 12:28 PM, Tim Hollebeek wrote:
>> I mean, this is a definitional thing, so there is no right answer, but C509 
>> is so close that I think trying to be a purist and claiming they are not 
>> X.509 just because they are not ASN.1 encoded will cause more problems than 
>> it solves.
>>  
>> Seeing C509 just as an alternative encoding for traditional ASN.1 certs, and 
>> that both of them basically encode the same X.509 profile(s) and follow 
>> similar rules makes more sense to me. So I would put them under the general 
>> PKIX umbrella.
>>  
>> It will also be easier to convince people to adopt them if people realize 
>> it’s just a different (and better!) encoding for the thing they already know 
>> and pretend to love.
>>  
>> -Tim
>>  
>> From: Göran Selander <[email protected]> 
>> <mailto:[email protected]>
>> Sent: Wednesday, October 8, 2025 9:56 AM
>> To: Tschofenig, Hannes <[email protected]> 
>> <mailto:[email protected]>; Sipos, Brian J. 
>> <[email protected]> <mailto:[email protected]>; [email protected] 
>> <mailto:[email protected]>
>> Subject: [COSE] Re: The term "PKIX" and C509
>>  
>>  
>> Hi,
>>  
>> C509 defines an invertible CBOR re-encoding of DER encoded X.509 
>> certificates, which supports large commonly used parts of RFC 5280 including 
>> RFC 7925, IEEE 802.1AR, CAB Baseline, RPKI, and eUICC profiled X.509 
>> certificates.
>>  
>> This doesn’t make C509 into X.509. But since the mapping can be reversed to 
>> obtain the original DER encoded X.509 certificate it can be used as a 
>> compact representation of X.509 certificates within the PKIX infrastructure.
>>  
>> Hope that helps!
>>  
>> Göran
>>  
>>  
>> From: Tschofenig, Hannes <[email protected] 
>> <mailto:[email protected]>>
>> Date: Wednesday, 8 October 2025 at 15:22
>> To: Sipos, Brian J. <[email protected] 
>> <mailto:[email protected]>>, [email protected] <mailto:[email protected]> 
>> <[email protected] <mailto:[email protected]>>
>> Subject: [COSE] Re: The term "PKIX" and C509
>> 
>> Hi Brian!
>>  
>> The term PKIX stands for Public-Key Infrastructure using X.509. Using it to 
>> refer to other technologies that do not use the same encoding as X.509 
>> certificates is likely to cause confusion. Note that PKIX also refers to the 
>> entire infrastructure – not just the format of the cert.
>>  
>> Just my two cents.
>>  
>> Ciao
>> Hannes
>>  
>> Von: Sipos, Brian J. <[email protected] <mailto:[email protected]>>
>> Gesendet: Mittwoch, 8. Oktober 2025 15:00
>> An: [email protected] <mailto:[email protected]>
>> Betreff: [COSE] The term "PKIX" and C509
>>  
>> WG,
>> >From the perspective of a user or a profile specification allowing the use 
>> >of X509 and C509 in, for example, COSE messages has there been any 
>> >discussion about terminology in the sense of the following:
>> Is it expected that the term “PKIX” will exclusively refer to X.509 as 
>> defined in RFC 5280? Or will PKIX be an umbrella term to include C509 as an 
>> equivalent encoding of the same information model? Possibly “public key 
>> certificate” is a better general purpose term, though a little more narrow 
>> in scope (a single credential) than what PKIX would imply (the whole PKI).
>>  
>> Any thoughts about this?
>> Brian S.
>> 
>> 
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