What does it mean that the .ORG Zone is “signed”?
Zone-signing is the process of cryptographically signing the authoritative data within a zone file. This process adds new records to the zone, which allows verification of the origin authenticity and integrity of data. Since the only observable effect of this operation is that new records are added, zone-signing. Key maintenance (key generation, storage, and rollover) is an addition to the zone-signing operation. The .ORG Zone has been NSEC3 (RFC 5155) signed.