Wireless Security Devised for Implanted Medical Devices

Engineers at Massachusetts Institute of Technology in Cambridge and University of Massachusetts in Amherst have designed a system that shields implanted medical devices like heart pacemakers and defibrillators from unauthorized wireless access or sabotage. Their findings will be presented at the ACM Special Interest Group on Data Communication (SIGCOMM) conference in Toronto, Canada in August.

Millions of people worldwide have implanted devices to regulate or monitor key health functions that take advantage of advances in miniaturization of electronics and wireless technologies. The wireless technologies, in particular, allow physicians to check or adjust the operation of the devices non-invasively, reducing cost and risks to the patient.

These same wireless capabilities, however, open a possible security risk to the patient: accidental or deliberate access to the device by unauthorized persons, with potential deadly outcomes. Computer scientist Dina Katabi and two graduate students comprised the MIT part of the team (with Kevin Fu of UMass) that designed a system for shielding implanted devices from unexpected wireless intrusion.

Implanted medical devices have special requirements and constraints that make adding security more of a challenge. Their small size and low-power design limit the amount of internal changes possible. The devices may also need to be accessed in an emergency, where encryption of signals would prevent access. And retrieving a key to decrypt signals would likely add delays to treating the patient, which could have dire consequences.

To meet these requirements, the MIT/UMass team devised a second transmitter to jam unauthorized signals in the device’s radio frequency, permitting only authorized users to communicate with it. The jamming transmitter, not the device itself, would handle encryption and authentication, thus allowing the shielding transmitter to work with existing implanted devices.

The shield transmitter, worn separately by the patient, uses simultaneous send and receive signals in the same frequency band. A new method of signal processing enables the shield to jam the device’s signal to unauthorized persons while not interfering with it for legitimate users.

“Think of the jamming signal that we are creating as a secret key,” Katabi explains. “Everyone who doesn’t know the secret key just sees a garbage signal.” Because the shield knows the shape of its own jamming signal, however, it can, in effect, subtract it from the received signal.

The researchers obtained second-hand implantable defibrillators from local hospitals that still had battery power, and conducted proof-of-concept tests with these devices using programmable radio transmitters to simulate the shield transmitter. The tests showed that the system effectively provides confidentiality for private data and protects the implantable device from unauthorized commands.

While the system may be technically feasible, the question arises of the system’s commercial viability, given there has not been a documented case of unauthorized hacking of an implanted device. That question may be answered shortly. The Food and Drug Administration and Federal Communications Commission are working on rules and guidelines to bring wireless technologies for health care to market, in which security is often a key concern.

Read more. Trial: Monitor Implant Lowers Heart Failure Hospitalization

Photo: Steve Winton/Flickr

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