A New Approach to Nuclear Warhead Verification Using a Zero-Knowledge Protocol

Abstract

Warhead verification systems proposed to date fundamentally rely on the use of information barriers to prevent the release of sensitive information. Measurements with information barriers significantly increase the complexity of inspection systems, make their certification and authentication difficult, and may reduce the overall confidence in the verifiability of future arms-control agreements. This article presents a concept for a new approach to nuclear warhead verification that minimizes the role of information barriers from the outset and envisions instead an inspection system that avoids the measurement of sensitive information, using a so-called zero-knowledge protocol. This is a protocol in which the data learned by one party (i.e., the inspector) allow him/her to verify that a statement is true (e.g., the inspected warhead is identical to an authenticated template), but does not reveal any additional information, e.g., does not leak any information that would help infer the design of the inspected warhead. There is a wide literature on zero knowledge proofs in the digital domain using cryptographic tools, and we draw on these ideas to achieve this in the physical domain. The proposed inspection system relies on active interrogation of a test object with 14-MeV neutrons, including both tomographic transmission measurements that are sensitive to warhead configuration, and scattering/fission measurements that are sensitive to material properties. The viability of the method is examined with MCNP Monte Carlo neutron transport calculations modeling the experimental setup.