OmanMkII

While it likely is spam for the majority of users, I imagine the mods are looking at de-federating an instance that fulfills a specific need for a small number (keeping alien.top users updated on reddit). Because of that, it will likely have a bit of push back to de-federate entirely vs. a request to create the ability to block users/platforms. Think of it like newsletters, we need the ability to unsubscribe/block them, but we shouldn't necessarily ban them outright.

The public part of it would be the RSA pubkey, likely linked with an identifier such as the SHA-256 hash of the email. You could quite easily have that ledger public and it would take millennia to crack any of the emails, much easier to use fuzzing with common words and names than trying wasting computing power for a single email. The whole point of blockchain is that it's an immutable public ledger which would actually suit this idea quite well.

You may find these concepts interesting (if you don't know them already) Recursion algorithms for graphs: https://en.wikipedia.org/wiki/Shortest-path_tree Dynamic programming: https://www.baeldung.com/cs/tabulation-vs-memoization