“We are living in a Wi-Fi surrounding environment every day, and the new system is as safe as those Wi-Fi devices,” he said. “The reader is about 5 milliwatts, even less than 1 percent of the radiation from our smartphones.” The system needs about 8 seconds to scan a heart the first time, and thereafter the monitor can continuously recognize that heart. The system, which was three years in the making, uses the geometry of the heart, its shape and size, and how it moves to make an identification. “No two people with identical hearts have ever been found,” Xu said. And people’s hearts do not change shape, unless they suffer from serious heart disease, he said. The new system has several advantages over current biometric tools, like fingerprints and retinal scans, Xu said. First, it is a passive, non-contact device, so users are not bothered with authenticating themselves whenever they log-in. And second, it monitors users constantly. This means the computer will not operate if a different person is in front of it. Therefore, people do not have to remember to log-off when away from their computers. Xu and collaborators will present the paper — “Cardiac Scan: A Non-contact and Continuous Heart-based User Authentication System” — at MobiCom, which is billed as the flagship conference in mobile computing. Organized by the Association for Computing Machinery, the conferernce will be held from Oct. 16-20 in Snowbird, Utah.