A mathematical trick designed by cryptographers could be a key tool in nuclear disarmament.

Current disarmament treaties limit the number of nuclear warheads that a country has deployed and ready to use. Future treaties may also place limits on stored ones, but a country could mock up a fake storage centre and destroy its missiles for show – while keeping its real stockpiles intact.

Radiation scans can verify that a non-deployed warhead is genuine, but would also reveal secret details, making nations unwilling to consent. "An expert can look at the radiation signature and essentially reverse engineer the design," says Alexander Glaser of Princeton University.

For a way to verify that a warhead marked for destruction is real without spilling a state's secrets, Glaser and his colleagues turned to a mathematical method that can prove something is true without revealing why it's true.

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