@Override
  public byte[] getPublicKey(ID mbr) {
    if (encrypt != null) {
      return encrypt.getPublicKey(mbr);
    }
    return null;
  }
returns the handler that should process the given message. The default handler is the
membership manager
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/messenger/JGroupsMessenger.java