Encrypted HFDL position reports

A system and related method for encrypting HFDL position reports of an aircraft involves determining the position of the aircraft based on signals received from navigational satellites and generating data packets based on the position and an aircraft identifier such as an ICAO address. The data packets are encrypted for transmission to HF ground stations as a position report normally would be (e.g., as a performance diagnostic packet or a frequency diagnostic packet). However, the encrypted position data can only be decrypted by a control key provided to traffic control authorities or a subscriber key provided to the aircraft owner or authorized personnel. Only holders of the control key or subscriber key may decode the aircraft position and track the aircraft's heading or position.

CROSS-REFERENCE TO RELATED APPLICATIONS

BACKGROUND

Embodiments of the inventive concepts disclosed herein are directed generally to a system and related method for encrypting position data of an aircraft transmitted via the High Frequency Data Link (HFDL) protocol. HFDL uses the unique properties of high frequency (HF) radio waves (waves in the spectral band between 2.0 MHz and 30 MHz) to propagate long-range data or voice communications through the ionosphere (c. 30-375 miles above the earth's surface) at variable frequencies and transmission speeds (300, 600, 1200, or 1800 bps) depending on current propagation conditions (e.g., atmospheric temperature or electron density). The HFDL infrastructure incorporates a network of dedicated HF ground stations (HGS), currently comprising 15 HGS worldwide, each having an effective radius around 3,000 NM and thereby providing overlapping coverage over six continents. The network of HGS allows for single-hop and multi-hop transmissions over great distances and through transoceanic airspace underserved, or unserved, by surveillance radar or automatic dependent surveillance-broadcast (ADS-B) services.

Aircraft tracking sites such as FlightAware (flightaware.com) or other aircraft situation display to industry (ASDI) vendors allow the general public to track the position, heading, destination, tail number, or other particular details of commercial and civilian flights in near-real time, based on data from traffic control radar, ADS-B transmissions to and from the aircraft, or aircraft data link services using HFDL or similar protocols (e.g., Aircraft Communications Addressing and Reporting System (ACARS) or satellite communications (SATCOM)). For example, a hobby-grade shareware program called PC-HFDL allows any end user with a home computer to decode HFDL data traffic. While FlightAware cannot decode HFDL, PlanePlotter (www.coaa.co.uk/planeplotter.htm) employs PC-HFDL to provide a graphic display of tracked aircraft similar to that provided by FlightAware, but including those aircraft reporting their position via HFDL.

Aviation customers may have valid business reasons for preventing the general public (in particular, their competitors) from tracking the positions or flight plans of their aircraft and making inferences therefrom. Currently, only two options are available to those wishing to block public tracking of their aircraft, both of which are associated with particular drawbacks. A request may be filed with the FAA to block entirely a given aircraft tail number (thereby preventing any tracking data for that tail number from being broadcast to ASDI vendors). Similarly, a customer may request selective blocking of a given tail number from an ASDI vendor (in which case tracking data is still broadcast to the vendor, but the vendor agrees not to display it). In the first case, an FAA source block prevents a party (or, e.g., interested friendly personnel such as administrative staff or family members) from tracking its own aircraft. In the second case, a party may be required to contact multiple vendors to achieve selective blocking; in addition, charges may be associated with this service.

SUMMARY

In one aspect, embodiments of the inventive concepts disclosed herein are directed to an apparatus for encrypting High Frequency Data Link (HFDL) position reports. The apparatus may include a position receiver for receiving signals from location satellites and determining a position of an aircraft based on the received signals. The apparatus may include processors for generating position data based on the determined position and a unique identifier of the aircraft. The apparatus may include a cryptographic engine for generating an encrypted position by applying one or more cryptographic keys to the position data; the encrypted position may be decrypted by either a subscriber key or a control key. The apparatus may include an antenna and a coupler for scanning the high frequency range for uplink and downlink frequencies. The apparatus may include an HF data radio for receiving position report requests from HF ground stations (via uplink frequency) and transmitting the encrypted position to the HF ground stations (via downlink frequency).

In a further aspect, embodiments of the inventive concepts disclosed herein are directed to an HFDL communications system. The system may include processors for receiving position data from a position receiver of an aircraft, the position data corresponding to a determined position of the aircraft, and generating data packets based on the position data and a unique identifier of the aircraft. The system may include a cryptographic engine for encrypting the data packets by applying one or more encryption keys, the encrypted data packets decryptable by a subscriber decryption key and a control decryption key. The system may include an HF data radio for receiving position report requests from HF ground stations via an HF uplink frequency and transmitting the encrypted data packets to the HF ground stations via an HF downlink frequency. The system may include an HF antenna and a coupler for scanning the HF range for the uplink and downlink frequencies.

In a still further aspect, embodiments of the inventive concepts disclosed herein are directed to a method for encrypting HFDL position reports. The method may include receiving aboard an aircraft, via an HF uplink frequency, a position report request from an HF ground station. The method may include determining a position of the aircraft via a position receiver. The method may include generating data packets based on the determined position and a unique identifier of the aircraft. The method may include generating encrypted position data by applying encryption keys to the data packets. The method may include scanning the HF range for uplink and downlink frequencies, and transmitting the encrypted position data to the HF ground station at the HF downlink frequency.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Broadly, embodiments of the inventive concepts disclosed herein are directed to a system and related methods for encrypting HFDL position reports. Periodic reports of an aircraft position and identifier may be encrypted so that the aircraft may not be publicly tracked. Position data may be accessed by both air traffic control services and interested parties (e.g., aviation customers) via decryption keys.

Referring toFIG. 1, an exemplary embodiment of a system100for encoding HFDL position reports may include an HF antenna102, an HF coupler104, an HF data radio106, a cryptographic engine108, and a controller110including one or more processors. The cryptographic engine108may be incorporated into the HF data radio106, or housed (108a) in an appliqué or similar bump-in-the-wire device linked to the connection (112) between the controller110and the HF data radio106. The controller110may receive position data (114) of an aircraft116aboard which the system100is embodied. The position data114may be generated by an onboard Global Navigation Satellite System (GNSS) receiver118(e.g., GPS, GLONASS, Compass, Galileo) or similar position receiver configured to determine a current position of the aircraft116based on navigational signals120received from GNSS satellites122. The controller110may generate data packets based on the received position data, each data packet including a determined position of the aircraft116and a unique identifier (e.g., an International Civil Aviation Organization (ICAO) address) assigned to, or otherwise specific to, the aircraft116.

The HF data radio106may include one or more transceivers124connected to the HF coupler104and HF antenna102and configured for voice or data communications. The HF data radio106(particularly the transceiver124and coupler104) may continually scan the HF range (2.0 MHz-30 MHz) for optimal uplink and downlink frequencies by which to communicate with one or more HF ground stations (HGS)126. In the alternative, the HGS126may signal the aircraft116with instructions, including uplink frequencies for receiving messages from the HGS126or downlink frequencies for transmitting messages thereto. Transmissions from the aircraft116to an HGS126may include position data. For example, when the aircraft116logs onto (e.g., establishes contact with) an HGS126, the aircraft may transmit frequency diagnostic information in response to a request from the HGS126. Furthermore, the aircraft116may transmit performance diagnostic information to the HGS126if polled by the HGS or, for example, if data space exists within an ACARS message. During periods of low activity or inactivity, e.g., transoceanic crossings, the HGS126may poll the aircraft116every 10 minutes (or more frequently, if desired) to confirm the position of the aircraft116.

Position data of the aircraft116may be encrypted by the cryptographic engine108/108afor transmission (e.g., as a frequency diagnostic packet or a performance diagnostic packet) to the HGS126. For example, the cryptographic engine108/108amay apply one or more encryption keys to the position data to generate encrypted position data. The encrypted position data may be incorporated into a frequency diagnostic packet or a performance data packet for transmission (128) by the transceiver124of the HF data radio106, at an HF downlink frequency scanned for by the HF coupler104.

Referring now toFIG. 2, an exemplary embodiment of a system100afor encoding HFDL position reports may be implemented and may operate similarly to the system100ofFIG. 1, except that the system100amay include two decryption keys, a control key130and a subscriber key130a, for decrypting the encrypted position data transmitted (128) by the aircraft116to the HGS126. The HGS126may receive transmissions (128) from the aircraft116as well as other HFDL transmissions (128a) from other aircraft within its operating area. The HGS may forward received transmissions to the appropriate air traffic control (ATC) facilities132, which may in turn forward the received information to ASDI vendors134or other end users136. In addition, ASDI vendors134and end users136may independently receive transmitted HFDL messages.

Encrypted position data transmitted by the aircraft116may be encrypted such that one of two types of decryption keys may decode the encrypted position data and locate the aircraft116. ATC facilities132may be in possession of a control key130, allowing the ATC facilities to accurately track the aircraft116for traffic control and separation purposes. A control key130may enable the ATC facility132to decode encrypted position information from multiple aircraft (transmissions128,128a); deriving therefrom the positions and identifiers (138,138a) of the aircraft116as well as other aircraft transmitting to a given HGS126. The control key130may be a universal or master key capable of decrypting transmissions from all aircraft, or include several sets of group or class keys, each group key corresponding to a specific subset of aircraft. End users136may purchase a subscriber key130athat allows the end users (administrative staff, family members, co-workers) to decode encrypted position data transmitted (128) to the HGS126by the aircraft116and only that aircraft, providing the end users136with accurate positions and identifiers (138) of the aircraft116. For example, the owner of each aircraft116may be issued, or may generate, a unique subscriber key130acorresponding to that aircraft alone. A subscriber key130amay be derived from, or mathematically tied in some way to, the 24-bit ICAO address issued to the aircraft116(and specific to its transponder equipment). ASDI vendors134and other parties without a subscriber key130amay have access to encrypted transmissions (128) from the aircraft116to the HGS126, but are blocked (140) from receiving position or identification information.

Referring now toFIG. 3, an exemplary embodiment of a method200for encrypting HFDL position reports according to the inventive concepts disclosed herein may be implemented by the system100in some embodiments, and may include one or more of the following steps. At a step202, an HFDL data radio of an aircraft receives (via its HF transceiver), at an uplink frequency in the HF range (2.0 MHz-30 MHz), a request for a position report from an HGS. For example, the HGS may request a frequency diagnostic packet or a performance diagnostic packet from the aircraft.

At a step204, a position receiver aboard the aircraft determines a position of the aircraft.

At a step206, the controller generates position data of the aircraft, based on the determined position and a unique identifier of the aircraft. For example, the unique identifier may include, or may be based on, the ICAO address of the aircraft.

At a step208, the cryptographic engine encrypts the generated position data by applying one or more encryption keys to the position data. The encrypted position data may be decryptable by either a control key (provided to the HGS or to an ATC facility connected thereto) or a subscriber key (which may be specific to the aircraft (and associated with its unique identifier (e.g., ICAO address)) and provided to an owner of the aircraft).

At a step210, the HF transceiver/coupler of the aircraft scans the HF range for an HF downlink frequency.

At a step212, the HF data radio (via the HF coupler and antenna) transmits the encrypted position data to the HGS at the determined HF downlink frequency. For example, the encrypted position data may be transmitted to the HGS as a frequency diagnostic packet or as a performance diagnostic packet.

As will be appreciated from the above, systems and methods according to embodiments of the inventive concepts disclosed herein may provide a low-SWaP-C and efficient means for business aviation customers to efficiently control access to the real-time tracking of their aircraft, preventing tracking information from reaching competitors while retaining the ability to track their own aircraft.