FYI: I just released 4.0.19.Final.
This changes the way ASYM_ENCRYPT disseminates the private shared group key to members, going from a pull- to a push-based approach  .
In combination with JGRP-2293 , this should help a lot in environments like Kubernetes or Openshift where pods with JGroups nodes are started/stopped dynamically, and where encryption is required.
The design is at .
Check it out and let me know if you run into issues.