Ensuring the Physical Security of Microelectronics
The colossal reliance on semiconductor chips by the military and commercial industry reaches across weapons, machines and systems that perform key defense and national security functions. And while the Defense Department and the industry use secure chips, they are expensive and hard to design. To remedy that, the Defense Advanced Research Projects Agency, known as DARPA, is looking to automatically include defense mechanisms into the design of microchips. The agency is creating tools to manage the supply chain custody throughout the life cycle of a microchip and increase the availability and economics of secure microelectronics.
The process tracks a chip from its manufacturing beginning to its last use, creating a birth certificate and verifying its authenticity along the way as it’s installed into systems, explains Serge Leef, program manager in DARPA’s Microsystems Technology Office.
Tackling the security of semiconductor chips means working on a microlevel, however, at sizes smaller than a grain of sand. “Authentication at the electronics level is not very common,” Leef observes. “There is some level of authenticity at the printed circuit board level, and there are devices that people can put on printed circuit boards to track authenticity. But those are typically cumbersome to incorporate into designs, and represent operational complexity and increased costs.”
DARPA’s research into microelectronics is part of the agency’s bold five-year, $1.5 billion Electronics Resurgence Initiative (ERI), with a lofty goal of helping to redefine the future of the microelectronics industry, according to the agency. The agency is endeavoring to establish an ecosystem to drive down costs and enable semiconductor manufacturers to respond to Defense Department chip security needs. Set forth in June 2017, the ERI began with initial funding of $75 million, but given the importance of defense industry microelectronics, the agency broadened the scope of the initiative a year later under the direction of the Office of the Secretary of Defense.
DARPA is establishing six new programs as part of Phase II of the ERI, including a designs-related program to ensure the security of sensitive electronics called the Automatic Implementation of Secure Silicon (AISS) program, which Leef is directing.
The program manager, who joined DARPA last year and has specialized in electronic design automation during his career, explains that AISS will run for four years, beginning in the fall, following DARPA’s contract selection of the proposals submitted by the industry in May. “We want to make security in chips as common as fluoride in water,” he stresses.
The AISS program will build on the success of another DARPA microelectronics program called SHIELD, or the Supply Chain Hardware Integrity for Electronics Defense program, which is in its final stages. Compared to existing security devices that start at 25 cents apiece, SHIELD, developed by DARPA and industry teams at Northrop Grumman and SRI International, “is smaller than a grain of sand and costs less than one penny,” Leef states.
The SHIELD system includes three components: a microchip, a reader and a cloud-based server/database, Leef says. For the first component, the research parties created a semiconductor chip they refer to as a dielet. The tiny integrated circuit, at 0.1 millimeters in size, contains 100,000 transistors that implement numerous security features, including a unique identity system, a cryptographic engine, key storage, a radio interface and an antenna.
At the time of manufacturing, each dielet is queried for its unique identity, using a so-called PUF or physically unclonable function. “A PUF is a mechanism that relies on manufacturing variations to compute a unique signature of each chip,” he notes. “It is like an issuance of a birth certificate or like your fingerprints, iris scan, your voice signature all put together. They are essentially guaranteed to be unique.”
All kinds of sensors are incorporated into the dielet. “It has very interesting countermeasures and tamper detection mechanisms,” Leef offers. “So if you’re trying to heat this thing up, it’ll know. If you try to X-ray it, it will know. It’s also designed in such a way that if some other party tries to remove it, it will either self-destruct or set off the sensors, and it will be known that authentication chain has been violated.”
The reader, the second component of the SHIELD system, resembles a wand that connects to a smartphone. The reader’s role is to find the dielet, he clarifies. “You touch it or come close to it with the wand-like instrument, and the radio waves coming out of the wand power the dielet and cause a dialogue to begin.” The third part of the system, the cloud-based server, which holds data about the chip, enrolls it into its system. The cloud-based server receives the identity data from the dielet and computes a challenge response pair and sends it back to the reader, which presents the challenge to the chip for verification.
After enrollment of an identified chip, the cloud-based server registers the chip as being authentic, and it will track its authenticity over time. “Then we would have another interaction with the server that verifies that this particular dielet was bound to this particular part,” Leef states. “In essence, you are tracking the life of it through the supply chain.”
DARPA and the program teams have successfully demonstrated the proof of concept for SHIELD—reaching technology readiness level 6—and they are looking for transition partners. Given that SHIELD can be used for general supply chain or authentication tracking, the possible applications are broad. “That can cover things from medications to rare wines to luxury goods,” Leef shares.
Immediate military applications could include microchip part provenance. One potential transition partner, a large defense contractor, is looking at using SHIELD to track parts. “In other words, [verifying] all the components that make up the complex systems of systems throughout the supply chain,” he offers.
Another potential application for SHIELD is with a major, next-generation Defense Department platform, Leef notes. “They are starting with a clean, blank piece of paper and they’re saying, ‘We want to do this right,’” he relays. “This is a program that’s going to run for decades, and [they are thinking], ‘We’re starting it now, so let’s use the most advanced technology we can find to start tracking the supply chain before we even design anything.’”
SHIELD also offers important capabilities to the commercial industry. “There are some semiconductor companies that already have security product lines and something like SHIELD fills a nice niche in their portfolio,” Leef adds. “So we’re working with some of them so that they can license the technology.”
And although SHIELD offers substantial advantages over existing chip authentication methods, for the future, with AISS, DARPA is looking at additional chip security measures outside of enrollment and authentication. “With silicon security, there’s probably two or three dozen things that we can do to make chips more secure,” Leef noted. “And so AISS will incorporate all of that stuff right into the chip. At the same time, it allows you to automatically synthesize chips that have embedded security.”
AISS will include a security partition that implements the on-chip security features, many of which are novel capabilities.
The research will provide key automation, flexibility and efficiencies in secure chip manufacturing, which is especially important since every chip does not need the same level of security, he stresses. And some chips with the highest security requirements may be larger and more expensive; they may draw more power or run slower. With AISS, the automation of including defenses into chip designs will help users gauge the appropriate level of trade-offs. The AISS system on a chip “will be automatically generated, integrated and optimized to meet the objectives of the application and security intent,” according to DARPA.
In addition, the agency and its selected industry teams will develop a new design flow for digital integrated circuits that protects advanced chips from four of the known cyber attack surfaces.
Attacks can come across the supply chain, or through a side channel in which adversaries try to listen to the emissions of the chip as it operates and deduce secrets, Leef suggests. Another attack surface is reverse engineering, where adversaries try to figure out the secret algorithms to discover something proprietary and confidential that may have competitive value or military secrets in which nation-states would be interested, he continues. The fourth attack surface is malicious hardware, where an adversary successfully embeds a malicious circuit into a chip and then, when triggered, unleashes a harmful payload.
“That’s what we’re trying to defend against in AISS,” Leef notes. “We’re trying to make it easy for people to include the defenses into the chip and also make it easy for them to trade off security against economics.”
Historically, these various attack surfaces have not been defended against, Leef warns. “Hardware today basically represents the last frontier,” he says. “If you can successfully attack the hardware, you can compromise huge volumes of devices.”
