NUCLEAR WEAPONSMonitoring Nuclear Weapons Stockpiles with Radio Waves

Published 1 November 2023

Monitoring whether states are complying with disarmament treaties is not an easy task. An international team has been exploring remote monitoring with the help of two antennas and a couple of mirrors.

An international research team has proposed a new method for monitoring nuclear disarmament treaties. The IT security experts developed a mechanism that uses radio waves to remotely monitor whether any changes are being made in a specific room. The researchers describe how robust and secure the approach is in the journal Nature Communications, published online on 17 October 2023. Teams from the Max Planck Institute for Security and Privacy (MPI-SP) in Bochum, Ruhr University Bochum, the School of Public and International Affairs at Princeton University, the University of Connecticut, Harvard University, PHYSEC GmbH, and Technische Universität Berlin collaborated on the development.

The researchers approached their project from a scenario in which State A wants to ensure that there are no changes in State B’s nuclear weapons stockpile – and to do so without permanent on-site monitoring. Specifically, a major threat is indicated by the removal of stored nuclear warheads to prepare them for deployment. “Our system uses two antennas to record a radio fingerprint of the room,” explains Dr. Johannes Tobisch, who earned his PhD on this research field in the CASA Cluster of Excellence at Ruhr University Bochum and MPI-SP and has since moved on to work in industry. One of the antennas emits a radio signal that is reflected off the walls and objects in the room. The other antenna records the signal. The recorded signal is characteristic: if the objects were moved only minimally, this would noticeably change the radio fingerprint. Major changes, such as the removal of a stored nuclear warhead, can thus be reliably detected.

Mirrors to Guarantee Security
However, this method can only work if state B measures the radio fingerprint at precisely the time when state A requests it. It’s therefore necessary to prevent State B from recording the radio fingerprint and sending the recording instead of a just-measured signal. “That would be like someone sticking a photo in front of a surveillance camera,” illustrates Johannes Tobisch.