UV-Ink Tattoos Could Encode Implantable Device Security Keys

Tattooed Ultraviolet (UV) reactive ink could offer a possible solution that would allow doctors to access implantable devices (IMDs) such as pacemakers and defibrillators when an unconscious patient needs emergency care.

Researchers at Microsoft (Redmond, WA, USA) have proposed that a user-selected human-readable key be encoded directly onto the patients skin by using UV-ink micropigmentation, adjacent to the point of implantation; to increase reliability the encoding could be augmented to include an error correcting code, or be replicated in full on the base of the patient's leftmost foot, at the arch. All devices used to communicate with the IMDs would be equipped with a small, reliable, and inexpensive ultraviolet light emitting diode (UV LED) and an input mechanism for key entry; a single key would be sufficient for multiple devices, and could be re-used when devices are replaced.

According to the proposal, UV micropigmentation would thus not advertise the presence of the IMD to potential attackers, unlike bracelets worn today that could also be lost. Another feature of UV micropigmentation is that it requires no day-to-day effort or notice from the patient, except more attention to the use of sunscreen to protect it. Pain as well would not be an issue, as the patients are already under local or general anesthesia to receive the implantation. The risk of serious infection due to a surgically performed skin-deep tattoo should also be significantly lower than that from the more intrusive implantation of a device.

The invisibility of UV micropigmentation under normal lighting also reduces the likelihood that it will be a signal detectable by others. When not covered by clothing, the UV ink can be hidden by UV-blocking sunscreen, since anyone close enough to read the tattoo is already close enough to kill the patient using forensically untraceable mechanisms. Also unlike bracelets, patients cannot forget their tattoo. The proposal was published on April 8, 2010, in Microsoft Research (please see related links below).

"To make an informed choice, patients will need to know the benefits and risks of both UV micropigmentation and the alternatives,” concluded report author Stuart Schechter, Ph.D. "Patients should also be aware of the fraction of patients issued medical bracelets who arrive at emergency departments without them.”

Life-critical implantable medical devices (IMDs) are becoming increasingly commonplace. The most familiar, the pacemaker, is implanted into a million patients each year in the United States alone. Recently, concerns have been raised about IMDs use of wireless protocols; the lack of authentication and integrity mechanisms put patients at risk from attack by anyone with a transmitter. Safeguards that use cryptographic authentication and integrity-protection require an access key available to authorized physicians, but not the attackers; however, emergency physicians cannot rely on patients to be in a conscious state and capable of providing access keys.

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