Personally, my reading between the lines on this subject as a non-expert is that we in the public might not know when post-quantum cryptography is necessary until quite a while after it is necessary.
Prior to the public-key cryptography revolution, the state of the art in cryptography was locked inside state agencies. Since then, public cryptographic research has been ahead or even with state work. One obvious tell was all the attempts to force privately-operated cryptographic schemes to open doors to the government via e.g. the Clipper chip and other appeals to magical key escrow.
A whole generation of cryptographers grew up in this world. Quantum cryptography might change things back. We know what papers say from Google and other companies. Who knows what is happening inside the NSA or military facilities?
It seems that with quantum cryptography we are back to physics, and the government does secret physics projects really well. This paragraph really stood out to me:
> Scott Aaronson tells us that the “clearest warning that [he] can offer in public right now about the urgency of migrating to post-quantum cryptosystems” is a vague parallel with how nuclear fission research stopped happening in public between 1939 and 1940.
How can we know that?
> Who knows what is happening inside the NSA or military facilities?
Couldn't have NSA found an issue with ML-KEM and try to convince people to use it exclusively (not in hybrid scheme with ECC)?
Things need to be rolled out in advance of need, so that you can get a do-again in case there proves to be a need.
(1) A PQ-secure way of getting the CRLs to the browser vendors. (2) a PQ-secure update channel.
Neither of these require broad scale deployment.
However, the more serious problem is that if you have a setting where most servers do not have PQ certificates, then disabling the non-PQ certificates means that lots of servers can't do secure connections at all. This obviously causes a lot of breakage and, depending on the actual vulnerability of the non-PQ algorithms, might not be good for security either, especially if people fall back to insecure HTTP.
See: https://educatedguesswork.org/posts/pq-emergency/ and https://www.chromium.org/Home/chromium-security/post-quantum...
[0] The situation is worse for Apple.
There are a number of "you"s here, including:
- The SDOs specifying the algorithms (IETF mostly)
- CABF adding the algorithms to the Baseline Requirements so they can be used in the WebPKI
- The HSM vendors adding support for the algorithms
- CAs adding PQ roots
- Browsers accepting them
- Sites deploying them
This is a very long supply line and the earlier players do indeed need to make progress. I'm less sure how helpful it is for individual sites to add PQ certificates right now. As long as clients will still accept non-PQ algorithms for those sites, there isn't much security benefit so most of what you are doing is getting some experience for when you really need it. There are obvious performance reasons not to actually have most of your handshakes use PQ certificates until you really have to.