Assessing the Security of a Navigation System: A Case Study using Enhanced Loran

Global Navigation Satellite Systems (GNSS) has become increasingly interwoven into the fabric of our infrastructure and economic system. However, as GNSS becomes more important for safety of life and economically critical infrastructure, subversive elements will be increasingly tempted to deny or spoof its signals. The fact that GNSS has vulnerabilities is well known and it is becoming recognized that back ups to GNSS are necessary [1]. Indeed, we are hopefully moving to a more comprehensive approach to position, navigation and timing (PNT) architecture. An element that should be central to the consideration is security. This paper examines the security capabilities of Loran as a case study for examining both a secure navigation system and a secure back up to GNSS. Loran, in particular the next generation Enhanced Loran (eLoran), has many properties that make it a good complement to GNSS. It has similar outputs and performance as GNSS. As it is an area navigation (RNAV) system, it can be used to drive the same interfaces as GNSS. eLoran is being developed to provide performance levels that can support non precision approach (NPA), harbor entrance approach (HEA), and stratum 1 frequency and precise timing. At the same time, it is an independent system and has failure modes that differ from GNSS. The attractiveness of Loran as part of a full PNT architecture has been recognized by the US Department of Homeland Security (DHS). In 2008, the DHS announced that eLoran will be implemented to provide “an independent national positioning, navigation and timing system that complements the Global Positioning System (GPS) in the event of an outage or disruption in service [2].” Europe has also recognized this with the General Lighthouse Authority (GLA) of England, Ireland, and Scotland also promulgating the development of eLoran for maritime use [3].