Pinning necessarily has to restrict the times a certificate can be changed because otherwise we have to solve a different problem &quot;How can I tell this new certificate is a good certificate&quot;.<p>You have proposed a solution to that second problem, let&#x27;s look at the threat model:<p>You adversary is:<p>* Capable of forcing or otherwise being able to create valid certificates.<p>* Has the capability to MITM nodes in a network.<p>The solution you have provided adds an additional hurdle for the adversary:<p>* must also be able to subvert your CA (or more generally, a specific CA - it doesn&#x27;t actually matter if you or someone else controls it - what matters is it is a specific root certificate).<p>So the browser, now TOFU&#x27;ing the initial certificate makes a note of the current certificate (and pins it) as well as the secondary signing CA (and also pins that).<p>When you want to rotate certificates you have your new cert signed by the two CA&#x27;s, one of which has to be the pinned CA.<p>I actually think this is a fairly elegant solution (for the operator), although it does come with some fairly large assumptions:<p>* If your adversary is large enough to be able to corrupt multiple CA&#x27;s (say a federal government) - then they are powerful enough to corrupt all your CA&#x27;s (even you - although, to be fair, if the can force you to do anything then the MITM capability is less interesting). So while this scheme benefits the operator, it provides negligible benefit to the client.<p>* You are reliant on the secondary CA to remain static (or having a backup CA) - this is the same problem as the original simply shifting the capability up one level - maybe this is OK.<p>Overall, this approach does provide more flexibility to the operator of the site - but provides no to negligible additional security on the client side (it upgrades the capability from being able to mimic any CA to being ale to mimic a specific CA), and may even put clients at greater risk - since there is now an additional avenue of certificate rotation which means extra code, extra verification to mess up etc.<p>These were a few thought that jumped into my brain - I would like to see a more detailed threat model &#x2F; paper exploring some new schemes as I think there are wins in this space that haven&#x27;t been realized yet - and there maybe improvements &#x2F; clarifications which can improve this model further.