Removing a CA section in usecases doc makes incorrect statements about what the Trust Expressions draft claims

[nharper]

The first source of pain comes from the existing websites which use the distrusted CA and now need to migrate to a new CA and renew their certificates. This typically requires a few months of notice to accomplish, but is largely a straightforward process. The Trust Expressions draft claims that this switchover could be made much faster or even instant. This is simply impossible.

The draft claims no such thing. https://www.ietf.org/archive/id/draft-davidben-tls-trust-expr-04.html#name-removing-cas states that the benefit Trust Expressions provides in distrust is a way to reduce the risk of a server operator switching to a new CA. What Trust Expressions allows for is a site operator to immediately start serving a new certificate chain to clients that have indicated (via Trust Expressions or another trust anchor negotiation mechanism) they trust that certificate chain, while continuing to serve the old certificate chain to other clients (regardless of whether those clients support Trust Expressions).

[dennisjackson]

Totally fair, that was bad wording on my part. I've adjusted the text to make it clearer.

[nharper]

The usecases doc still contains the problematic text:

The first source of pain comes from the existing websites which use the distrusted CA and now need to migrate to a new CA and renew their certificates. This typically requires a few months of notice to accomplish, but is largely a straightforward process. The Trust Expressions draft claims that this switchover could be made much faster or even instant. This is simply impossible.

I can't find any section in the Trust Expressions draft that makes this claim. In my first comment I found similar text in the draft and explained what it means (which is different from what is claimed in this text). Please remove this language or provide a citation.

[dennisjackson]

This is described in the explainer, split between several sections:

• Removing CAs
• Conflicting Relying Party Requirements
• Backup Certificates
• Public Key Pinning

[nharper]

I read those sections in the explainer, and only the "Backup Certificates" section comes close to saying "this switchover could be made much faster or even instant".

From the explainer:

Backup Certificates

A subscriber may obtain certificate paths from multiple CAs for redundancy in the face of future CA compromises. If one CA is compromised and removed from newer relying parties, the TLS server software will transparently serve the other one.

This refers to a specific case where a server operator chooses as part of their normal operations to obtain certificates from multiple CAs. In that specific case, with clients that support trust anchor negotiation, if one of those CAs gets distrusted, then once the effective-of date of the distrust passes, their servers will stop using the certificate chain(s) from the distrusted CA. Doing so is not impossible as you say.

Further, this is stating that a server operator can easily switch from one CA to another by using trust anchor negotiation. It's not stating that a root program can skip the "few months of notice".

The language "The Trust Expressions draft claims that this switchover could be made much faster or even instant. This is simply impossible." needs to be removed.