An international team of researchers has worked out a way to take highly secured and highly precise snapshots of the contents of any room. Using radio antennas and mirrors, it is possible to create "radio fingerprints" so precise to notice an object displacement of just a few millimeters. This tech could have a lot of applications but the team had nuclear weapons in mind.

In particular, their focus was on the monitoring of nuclear disarmament treaties. Their method allows for remote monitoring of facilities where nuclear weapons are to be stored. The system could easily tell if any weapons have been moved and doesn’t require inspectors to get on the ground.

“Seventy percent of the world['s] nuclear weapons are kept in storage for military reserve or awaiting dismantlement,“ co-author Dr. Sebastien Philippe from Princeton University said in a statement. “The presence and number of such weapons at any given site cannot be verified easily via satellite imagery or other means that are unable to see into the storage vaults.”

“Because of the difficulties [in monitoring] them, these 9,000 nuclear weapons are not accounted for under existing nuclear arms control agreements. This new verification technology addresses this long-standing challenge and contributes to future diplomatic efforts that would seek to limit all nuclear weapon types.”

The simplest setup for the system is made of two antennas. One emits the radio waves, which bounce around the walls of the room and objects present, and the other receives them. Now this setup works great to make a radio fingerprint – as long as you are sure that the people that own the facility are trustworthy. Because the radio fingerprint doesn’t come with a timestamp, it needed something more to work in different situations.

The team employed 20 rotating mirrors installed in a room that was being monitored. Having the mirror in changeable specific positions allows an extra level of security that can be used to strengthen the radio fingerprint approach.

In a field test, the system was deployed in a container with barrels that could be moved. A movement of just a few millimeters would show up in the fingerprint, which was an excellent result. The team also tested if an AI algorithm could decipher the connection between mirror positioning and radio fingerprints. It turns out that it could, but that it couldn't do it quickly.

“With 20 mirrors, it would take eight weeks for an attacker to decode the underlying mathematical function,” lead author Johannes Tobisch added. “Because of the scalability of the system, it’s possible to increase the security factor even more.”

The study is published in the journal Nature Communications.