in src/main/java/org/apache/sling/discovery/base/connectors/ping/TopologyRequestValidator.java [591:599]
private void checkActive() {
if (deactivated) {
throw new IllegalStateException(this.getClass().getName() + " is not active");
}
if ((trustEnabled || encryptionEnabled) && sharedKey == null) {
throw new IllegalStateException(this.getClass().getName()
+ " Shared Key must be set if encryption or signing is enabled.");
}
}