DHS Builds Position, Navigation and Timing Framework

Over the next year, U.S. government officials intend to develop an initial conformance framework to ultimately improve resilience for systems that provide positioning, navigation and timing for a wide variety of users. That initial framework will focus on timing, and lessons learned will be used to develop more comprehensive versions.

Accurate position, navigation and timing (PNT) is essential for the proper function of much of the nation’s critical infrastructure. Traffic signal lights, aircraft, automatic teller machines and military operations all depend on it, mostly in the form of Global Positioning System (GPS) satellite signals. Precise timing is one aspect that is particularly important. Some critical infrastructure systems, including the electric grid, communication networks and financial institutions, require synchronization within one microsecond or better, according to a fact sheet provided by the Department of Homeland Security’s (DHS’s) Science and Technology Directorate.

However, GPS’s space-based signals are low power and unencrypted, making them susceptible to both intentional and unintentional disruption, the DHS fact sheet explains.

Jammers, which are illegal to market, sell or use in the United States, present one problem. They can block a wide array of legal communications, including 911 calls and communications among first responders.

In 2013, a New Jersey man who worked for an engineering company was fined nearly $32,000 after the jamming device in his pickup truck interfered with Newark Liberty International Airport’s satellite-based tracking system. Commercial drivers have been known to use jamming devices so that they cannot be tracked by employers. Spoofing, though less frequent than jamming, also is a concern.

A government-sponsored study by RTI International has found that a GPS outage lasting 30 days could cost the U.S. economy $1 billion each day. And the reliance on GPS signals is expected to increase dramatically as the nation moves toward smart cities, autonomous automobiles and next-generation communications. “There’s a huge market out there for location-based services. That market is growing rapidly. The companies like to be able to tell exactly where you are with your phone or with your car,” says James Platt, the PNT chief at the National Risk Management Center within the DHS Cybersecurity and Infrastructure Security Agency (CISA). “We need to stay involved with them so that they understand as they integrate those things, what the vulnerabilities are.”

DHS officials assess the vulnerabilities, develop technical solutions and best practices, and engage and inform industry and critical infrastructure owners on the risks and potential mitigations. DHS is working with the Department of Transportation on the Resilient PNT Conformance Framework, which will address needs for civil PNT systems. The framework is expected to help companies build more resilient PNT systems, including GPS receivers. It also will help users of such systems develop tactics, techniques and procedures and employ best practices to better secure PNT systems.

The DHS also has shared its plans with other agencies at PNT working group meetings. The initial framework will address timing receivers, but DHS officials have invited Department of Transportation and Federal Aviation Administration officials to participate so that lessons learned can be effectively incorporated into later versions, which will focus on position and timing.

“The first framework is really going to focus on timing receivers because it’s a little bit easier. Timing receivers don’t move,” Platt notes. “We’re going to focus on timing first and then use what we learn from the timing aspects to inform what we do with position and navigation.”

DHS officials convened a working group this summer. The Science and Technology Directorate is funding participation and support from the Homeland Security Systems Engineering and Development Institute and the National Institute of Science and Technology’s Boulder Laboratories. “We will be working for the next six months with the goal of transitioning to a standards development organization in late fiscal year 2020 to develop a formal standard,” reports Brannan Villee, PNT project manager within the DHS Science and Technology Directorate.

Ernest Wong, PNT technical manager, Technology Centers Division, Science and Technology Directorate, explains the process. “There are two steps here. For the timing piece, first we have to develop some general guidelines.”

After that, the department will develop specific requirements to help validate that PNT systems perform as promised. “Hopefully, given that we’re going to have some guidelines beforehand and have some idea of where we want to go, that will help accelerate that second part,” Wong adds.

The Resilient PNT Conformance Framework likely will establish different levels of resiliency, such as levels one, two, three and four. That will allow different end users to implement solutions that best fit their needs. A telecommunications network, for example, may not need as much security or resiliency on the outer edges as it does at the central office. “We recognize those differences, and we’re trying to set different levels of resilience. Hopefully this will both help inform risk management for end users and also help vendors and manufacturers to differentiate their products,” Wong says.

Villee stresses the importance of government personnel working closely with the private sector. “It’s so critical as we work on our Resilient PNT Conformance Framework, that we’re working with people who are manufacturers and people who are users in critical infrastructure sectors, such as telecom, finance and power grids. People have different needs, and we want to ensure that we develop a framework that’s going to be applicable across all those critical infrastructure subsectors.”

In addition to building the framework, DHS officials are developing technologies to improve critical infrastructure PNT resiliency. For example, the Total Horizon Nuller antenna, which was developed in conjunction with the Homeland Security Systems Engineering and Development Institute, is available to manufacturers through a no-cost license. The system, a specialized low-cost, anti-jam GPS antenna, has transitioned to multiple companies for commercialization.

The department also is developing new techniques for detecting false signals. “There are also detection algorithms that we’re working on, so you can look at things like power levels and multiple peaks [of a signal]. If you can understand the characteristics of the signal, you can identify what doesn’t look quite right,” Wong says. “Some of the spoofing detection items we have will probably be available sometime in 2020.”

Furthermore, DHS hosts a series of test opportunities for stakeholders and industry to test equipment in unique “live-sky” signal environments that include GPS interference. “What we do on these test events is we provide a live-sky GPS spoofing environment for participants. That’s not something they can do by themselves,” Wong states. “Even as a government agency, we have to jump through a lot of hoops to be able to do that.” The events were held in 2017 and 2018. A government shutdown resulted in the cancellation of the 2019 event, but another is expected in 2020.

The critical infrastructure is mostly owned by the private sector, and the government cannot tell those owners what to do. But as part of the effort to keep the private sector informed, officials emphasize that GPS is not the only solution and is not always the best solution. For instance, Platt cites a phenomenon known as multipath in which GPS signals bounce off of the containers in the container yards at ports, making it difficult to obtain a precise location. “You have to do a lot of math that I’m not capable of doing to figure that out, but GPS maybe is not the greatest system for that,” Platt explains. “Other systems are designed to compensate for that, so it may be more beneficial to go with those other systems.”

Still, other options can have both pros and cons as well. “Those other systems may or may not have software vulnerabilities you’re not aware of. Don’t just blindly assume something is better than GPS. Do your research, understand the risk and make a well-informed risk decision.”

Wong says GPS alternatives generally fall under three broad categories: global, regional and localized. He cites so-called pseudo-satellites, which are ground-based transmitters emitting GPS-like signals. Other terrestrial systems may use non-GPS signals.

Another method, the radio station WWVB, located near Fort Collins, Colorado, and provided by the National Institute for Standards and Technology, is one alternative or complementary system for timing. The station’s broadcasts are used to synchronize consumer electronic products such as wall clocks, clock radios and wristwatches. Additionally, WWVB may be used in other consumer timekeeping applications, including appliances, cameras and mobile apps. “Imagine if everyone is using GPS and something happens to GPS. Everything goes down.” Platt notes. “We’re aware of a lot of [other systems]. They all have different characteristics, different pros and cons, so they apply to different particular end users in critical infrastructure. It’s not one size fits all.”

Platt calls GPS “one of the greatest systems ever built,” but says that any unencrypted signal should be double checked. “If it’s being broadcast in the frequency spectrum, it’s subject to interference, disruption and corruption. Build your systems with that in mind,” he advises. “Any time you’re using an unencrypted signal that’s coming through the spectrum, you should be wary—if you have a critical application—that the signal is coming from who you think it’s coming from.”