This is exactly correct. The answer is that we should build better routing into OpenSSL - and all the other PKI-validating products. It's complex and complicat

This is exactly correct. The answer is that we should build better routing into OpenSSL - and all the other PKI-validating products. It's complex and complicated, but if you only have a very narrow and particular purpose (e.g. just care about TLS), then you can get away with it with rather a little amount of code, as Mozilla's mozilla::pkix shows - https://blog.mozilla.org/security/2014/04/24/exciting-updates-to-certificate-verification-in-gecko/ https://blog.mozilla.org/security/2014/04/24/exciting-update... But even if we were to change all systems tomorrow, that affects only the upper 10% or, to be generous, 25% of PKI clients (nb: numbers pulled out of my ass, but it's an experienced ass). We still have a LONG tail of systems running OpenSSL, earlier versions of Windows, or any number of custom solutions, and they support SHA-256 but won't ever be updated again. So stopping SHA-1 actually protects them, and is the only thing that CAN possibly protect them, and that's why LV is such a hard trade-off: we give up the protections for a large chunk of users, in order to regain access to a small group. And that's ignoring that the data quantifying the size of the small group, or _why_ the small group exists (to see if there are other levers or alternatives than "replace device" and/or "keep issuing SHA-1" exist. Luckily, Jan 1 isn't going to be some SHApocolypse - 39 month certs issued on Dec 31 2015 will remain valid well into 2019, so there's time to have a reasoned, data-driven debate about "old-old" clients, "new-old" clients, and "new-new" clients.