Nuclear weaponsOvercoming the trust barrier in nuclear weapons verification measurements

Published 9 June 2017

Trust but verify. The catchphrase for arms control popularized by President Ronald Reagan sounds simple. However, verification involving sensitive data is a very complex endeavor. Verifying that a nuclear warhead actually is a warhead may include confirming key attributes. But the act of confirming certain technical attributes might reveal critical design information — closely guarded national secrets for any country. Confirming these attributes will likely require overcoming the hurdle of protecting sensitive design data. Sandia National Laboratories physicist Peter Marleau has developed a new method for verifying warhead attributes.

Trust but verify. The catchphrase for arms control popularized by President Ronald Reagan sounds simple. However, verification involving sensitive data is a very complex endeavor.

Verifying that a nuclear warhead actually is a warhead may include confirming key attributes. But the act of confirming certain technical attributes might reveal critical design information — closely guarded national secrets for any country. Confirming these attributes will likely require overcoming the hurdle of protecting sensitive design data.

Sandia Lab says that Sandia National Laboratories physicist Peter Marleau has developed a new method for verifying warhead attributes. Called CONFIDANTE, for CONfirmation using a Fast-neutron Imaging Detector with Anti-image Null-positive Time Encoding, the method could help address the problem of conducting verification measurements while simultaneously protecting sensitive design information. CONFIDANTE provides middle ground for the warhead owner, or host, who wants to protect sensitive information, and the monitor, who may be seeking to verify that sensitive information to confirm the inspected item is a warhead.

“CONFIDANTE is an implementation of a zero-knowledge proof (ZKP) as a way to demonstrate the validity of a claim while providing no further information beyond the claim itself,” explained Marleau. “Unlike other ZKP confirmation methods, which rely on a measuring instrument that has been pre-loaded with sensitive information, CONFIDANTE allows the monitoring party to conduct the measurement in real time without accessing sensitive design data.”

Overcoming the trust barrier with ZKP
About three years ago, the Department of Energy’s Princeton Plasma Physics Laboratory and Princeton University developed a ZKP object-comparison system to potentially support warhead confirmation while protecting sensitive design data. In mathematical cryptography, ZKP is accomplished by challenging a host to solve a problem that is only possible if the host possesses the information being authenticated. After repeated challenges, the host can prove it possesses that information without revealing any details about the information itself.

In the Princeton group’s ZKP implementation, confirmation that an alleged warhead has the characteristics of a warhead is demonstrated through neutron transmission and emission counts measured by an array of radiation detectors. To protect sensitive design data during the measurement process, the Princeton method prepares the radiation detectors with a template rather than directly comparing in real time the images of a warhead being verified with a trusted warhead.