*** John Goerzen [2021-08-17 16:04]:
>A <-> B <-> [C, D, E]
>[...]
>Have I got that right?

Yes, everything you wrote is correct.

>So, for a setup like this, it is most efficient to have the "untrusted"
>relay node B be part of the area, but lack the keys.

Yep, also right. The first setup you described (with "keyless" B-node)
is the most efficient from the point of less possible duplicated messages.

-- 
Sergey Matveev (http://www.stargrave.org/)
OpenPGP: CF60 E89A 5923 1E76 E263  6422 AE1A 8109 E498 57EF