Year
2017
Abstract
Nuclear arms-control treaty verification tasks such as warhead authentication, or counting and tracking treaty accountable items in sensitive facilities, require both trusted and highly secure sensors and measurement equipment on site. Since the involved parties are mutually distrustful, and powerful enough to carry out cutting-edge, high-cost attacks on the sensors and equipment,standard electronic security techniques based on vulnerable digital secret keys may no longer be applicable. Here, we propose and demonstrate a radically new approach to trusted sensors for nuclear measurements that does not require classical tamper-resistant hardware nor cryptographic keys for data certification. We show that a non-electronic, passive superheated emulsion detector can be treated as an optical physical unclonable function sensitive to nuclear radiation, overcoming many of the abovementioned issues. These emulsions are stable over time, but their random structure is irrecoverably changed after being exposed to neutron irradiation. In this paper, we show that they meet the basic requirements of a sensor physical unclonable function, a recently emerging, new cryptographic and security primitive. To do so, we direct coherent light at the emulsions and observe the scattering events by the randomly suspended drops. From the resulting unique transmitted patterns, we extract bit strings or “sensor responses”, which can prove or disprove that the state of the sensor has been altered by neutroninteraction. We further demonstrate the desired rapid and reproducible decorrelation of the responses with respect to the transverse and angular motion of the laser beam, as well as the irrecoverable physical alteration of the entire sensor through the exposure of the emulsion to 14-MeV neutrons. Given these properties, superheated emulsions are promising candidates for nuclear arms control verification protocols requiring trusted sensors.