Researchers have created technology that is 10 times more reliable than current methods of producing unclonable digital fingerprints that can be used to authenticate devices linked to the Internet of Things (IoT).
The physically unclonable function (PUF) technology generates two unique fingerprints for each PUF. This “zero-overhead” method uses the same PUF components to make both keys and does not require extra area and latency because of a design feature that also allows the PUF to be about 15 times more energy efficient than previously published versions. Each PUF unit can work in two modes. In the first mode, it creates one fingerprint, and in the other mode it gives a second fingerprint. Each one is a unique identifier. If the device fails in the first mode, it can use the second key.
Each transistor on a computer chip is incredibly small. More than a billion of them can be crammed onto a chip half the size of a credit card. But for all their precision, microchips are not perfect. The difference between transistors can amount to a few more atoms in one or a few less in another, but those minuscule differences are enough to produce the electronic fingerprints used to make PUF keys.
For a 128-bit key, a PUF device would send request signals to an array of PUF cells comprising several hundred transistors, allocating a 1 or 0 to each bit, based on the responses from the PUF cells. Unlike a numeric key that's stored in a traditional digital format, PUF keys are actively created each time they're requested, and different keys can be used by activating a different set of transistors.
Adopting PUF would allow chipmakers to inexpensively and securely generate secret keys for encryption as a standard feature on next-generation computer chips for IoT devices. Measuring just a few millimeters in size, the latest IoT prototypes can pack a processor, flash memory, wireless transmitter, antenna, one or more sensors, batteries, and more into an area the size of a grain of rice.
The PUF keys are created using a static voltage rather than by actively powering up the transistor. It's counterintuitive that the static approach would be more energy efficient because it's the equivalent of leaving the lights on 24/7 rather than flicking the switch to get a quick glance of the room.
Although the PUF module is always on, it takes very little power — even less than a conventional system in sleep mode. The design occupies 2.37 square micrometers to generate one bit on prototypes produced using 65-nanometer complementary metal-oxide-semiconductor (CMOS) technology.