A farewell to (nuclear) arms: A novel technique could facilitate nuclear disarmament
No classified data would be measured in this process, and no electronic components that might be vulnerable to tampering and snooping would be used. “This approach really is very interesting and elegant,” said Steve Fetter, a professor in the School of Public Policy at the University of Maryland and a former White House official. “The main question is whether it can be implemented in practice.”
PPPL project
A project to test this approach is under construction at PPPL. The project calls for firing high-energy neutrons at a non-nuclear target, called a British Test Object, that will serve as a proxy for warheads. Researchers will compare results of the tests by noting how many neutrons pass through the target to bubble detectors that Yale University is designing for the project. The gel-filled detectors will add the neutrons that pass through to those already preloaded to produce a total for each test.
The project was launched with a seed grant from The Simons Foundation of Vancouver, Canada, that came to Princeton through Global Zero, a nonprofit organization. Support also was provided by the U.S. Department of State, the DOE (via PPPL pre-proposal development funding), and most recently, a total of $3.5 million over five years from the National Nuclear Security Administration.
Glaser hit upon the idea for a zero-knowledge proof over a lunch hosted by David Dobkin, a computer scientist, and until June 2014, dean of the Princeton faculty. “I told him I was really interested in nuclear warhead verification without learning anything about the warhead itself,” Glaser said. ‘“We call this a zero-knowledge proof in computer science,”’ Glaser said Dobkin replied. “That was the trigger,” Glaser recalled. “I went home and began reading about zero-knowledge proofs,” which are widely used in applications such as verifying online passwords.
Disguising information
Glaser’s reading led him to Boaz Barak, a senior researcher at Microsoft New England who had taught computer science at Princeton and is an expert in cryptology, the science of disguising secret information. “We started having discussions,” Glaser said of Barak, who helped develop statistical measures for the PPPL project and is the third coauthor of the paper in Nature.
Glaser also reached out to Goldston, with whom he had taught a class for three years in the Princeton Department of Astrophysical Sciences. “I told Rob that we need neutrons for this project,” Glaser recalled. “And he said, ‘That’s what we do — we have 14 MeV [or high-energy] neutrons at the Laboratory.’” Glaser, Goldston and Barak then worked together to refine the concept, developing ways to assure that even the statistical noise — or random variation — in the measurements conveyed no information.
The release notes that if proven successful, dedicated inspection systems based on radiation measurements, such as the one proposed here, could help to advance disarmament talks beyond the New Strategic Arms Reduction Treaty (New START) between the United States and Russia, which runs from 2011 to 2021. The treaty calls for each country to reduce its arsenal of deployed strategic nuclear arms to 1,550 weapons, for a total of 3,100, by 2018.
Not included in the New START treaty are more than 4,000 nondeployed strategic and tactical weapons in each country’s arsenal. These very weapons, note the authors of the Nature paper, are apt to become part of future negotiations, “which will likely require verification of individual warheads, rather than whole delivery systems.” Deep cuts in the nuclear arsenals and the ultimate march to zero, say the authors, will require the ability to verifiably count individual warheads.
— Read more in Alexander Glaser et al., “A zero-knowledge protocol for nuclear warhead verification,” Nature 510 (26 June 2014): 497-502 (doi:10.1038/nature13457)
