Support transitive trust for E2E verification between users (i.e. web-of-trust) in some situations

https://news.ycombinator.com/item?id=19167585 points out that there may be legitimate times where you want to avoid O(N^2) verifications between a set of users - e.g. verifying people in a physically secure setting such as an office or conference.

For that matter, if you join a company, it'd be nice if you only had to verify your boss, and then transitively trust the rest of the company.

I vaguely remember that cross-signing is actually considering this use case somehow, but am failing to find/remember how?

Start by reading the linked Hacker News discussion and reviewing how Matrix cross-signing addresses this use case. Define the trust-transitivity scenarios and protocol behavior before implementation; done requires an agreed design for safely reducing pairwise E2E verification.

Written by the indexing model from the issue text.