Thanks for reading!
Indeed, if people take one thing away from this article, it should be that the name in CA certificates is meaningless.
Indeed, if people take one thing away from this article, it should be that the name in CA certificates is meaningless.
If I could suggest another article subject that I think very few people are aware of and would make good hay.
How certificate SKIDs work, and why everyone can tell from the transparency logs every time you reuse your private key and every certificate ever issued to that SKID.
Not a bad idea to write a post about SKID because everyone misunderstands it! It does not reliably identify a key, since CAs are allowed to derive it however they want. If you want to find other certificates using the same key, you should ignore the SKID entirely and instead search based on the hash of the SubjectPublicKeyInfo. (In fact, starting September 15, inclusion of the SKID in website certificates will be NOT RECOMMENDED.)
Do you know if the dis-recommendation of SKIs also applies to AKIs? I know they’re similarly (but slightly less) flexible, so moving away from them would (seem) to be a win as well.
That said, they all suffer from the same problem - they look like they're derived from the public key, but there's no guarantee of this. Their only use is as an opaque identifier for looking up the issuer of a certificate, and only some certificate validators use them (e.g. Microsoft's); other validators (e.g. Mozilla's) ignore AKI/SKI entirely and just look up issuers by subject name, which works completely fine, suggesting that AKI/SKI are unnecessary.