[Rhinobird]

Can any of this be beaten into a way to verify group membership?

Say you want to prove you are a member of the AMA or IEEE, or Bar? Could you set up a large group for the association and their communications, and then when asked provide verifiable credentials that you are a member? Like a group membership signature?

[namibj]

Have the group sign a pubkey of yours. Use said pubkey. Add revocation lists.