RFC 9849 - Encrypted Client Hello

Now that ECH is standardized I started to look into it to understand what's coming. While generally desirable to not leak the SNI information, I'm not sure if it will ever make it to the masses of (web)servers outside of big CDNs. Beside of the extension of the TLS protocol to have an inner and outer ClientHello, you also need (frequent) updates to your HTTPS/SVCB DNS records. The idea is to rotate the key quickly, the OpenSSL APIs document talks about hourly rotation. Which means you've to have encrypted DNS in place (I guess these days DNSoverHTTPS is the most common case), and you need to be able to distribute the private key between all involved hosts + update DNS records in time. In addition to that you can also use a "shared mode" where you handle the outer ClientHello (the one using the public key from DNS) centrally and the inner ClientHello on your backend servers. I'm not yet sure if that makes it easier or even harder to get it right. That all makes sense, and is feasible…