> Imagine you have a VPN server with 200 road warrior clients somewhere out there in the world - which is a very normal use-case. If you were to change the ciph

> Imagine you have a VPN server with 200 road warrior clients somewhere out there in the world - which is a very normal use-case. If you were to change the cipher you are using from one day to the next one, you would need to upgrade your WireGuard software on all those laptops, phones, etc. at the same time. That is literally impossible. Administrators who have tried this needed months to deploy configuration changes. Sometimes even middle-sized companies need years to conduce a process like this. In a world where Mario Kart Tour can get millions of people on all sorts of smartphones to update within a day of release, there is no actual reason why anyone else should be unable to. All of these businesses have painted themselves into a corner - they've said that they don't care about being able to update software within a year, and they've built processes around that, and now they whine that they can't update software within a year. Tough. Design things from day one with the assumption that updates will happen. Then you can patch software vulnerabilities in a timely fashion and not get attacked via well-known VPN software flaws like Travelex did. If you genuinely care about your business, you'll already want to figure this out. (Which is the other problem with this article: "secure" isn't really about cryptographic algorithms, these days. There are tons of good cryptographic algorithms. Just don't use the bad ones. "Secure" is about whether you're using them right, whether you've got memory safety vulnerabilities, whether you've got logic flaws, etc. Every piece of complexity in your software - including cryptographic agility - imperils "secure," and the best defense is being able to confidently apply patches to your software wherever it's being run.)