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Alexander GlaserDepartment of Mechanical and Aerospace Engineering and Woodrow Wilson School of Public and International Affairs
HOW TO KEEP A SECRETNEW APPROACHES TO TRUSTED RADIATION MEASUREMENTS FOR NUCLEAR WARHEAD VERIFICATION
Technische Universität Darmstadt, 8. Juli 2016
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
CURRENT AREAS OF RESEARCH
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Verification of Nuclear Arms Control Treaties
Can one dismantle an atomic bomb without learning anything about its design?
Nuclear Energy and Nuclear ProliferationCan one safely expand the use of nuclear power without increasing the risk of nuclear proliferation?
Nuclear Energy and Climate Change
Are there new reactor technologies that could be potential “game changers” for nuclear power?
nuclearfutures.princeton.edu
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
CONSORTIUM FORVERIFICATION TECHNOLOGY
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Five-year project, funded by U.S. DOE, 13 U.S. universities and 9 national labs, led by U-MICH
Princeton participates in the research thrust on disarmament research (and leads the research thrust of the consortium on policy)
LANL
U Illinois
(not shown: U Hawaii)U Florida
NC State
Princeton and PPPLColumbia
YaleMIT
U MichiganU Wisconsin
Sandia
INL
PNNL
Oregon State
NNSS DukeORNL
LLNLLBNL
Sandia
Penn State
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
INTERNATIONAL PARTNERSHIP
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www.state.gov/t/avc/ipndv
FOR NUCLEAR DISARMAMENT VERIFICATION
Working Group One: “Monitoring and Verification Objectives” (chaired by Italy and the Netherlands) Working Group Two: “On-Site Inspections” (chaired by Australia and Poland)
Working Group Three: “Technical Challenges and Solutions” (chaired by Sweden and the United States)
Established in 2015; currently 26 participating countries (including Germany)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
RELEVANT NUCLEARARMS CONTROL TREATIES
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NUCLEAR NON-PROLIFERATION TREATYBans the acquisition of nuclear weapons by non-weapon states and commits the five weapon states to nuclear disarmament; verified by IAEA safeguards
Bans all nuclear explosions in all environments and would be verifiedby extensive verification mechanisms (International Monitoring System, CTBTO)
COMPREHENSIVE TEST BAN TREATY
At a minimum, treaty would ban fissile material production for weapons purposes; Issue about treaty scope: Would it also cover existing stocks?
FISSILE MATERIAL (CUTOFF) TREATY
NEXT-GENERATION NUCLEAR DISARMAMENT TREATIESAgreements that place limits on total number of nuclear warheads in arsenals would pose qualitatively new verification challenges
CONFIRMING THE AUTHENTICITY OF A NUCLEAR WARHEAD
(WHILE LEARNING NOTHING ABOUT IT)
(START CALIBRATION AND/OR TEMPLATE ACQUISITION)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
THOUSANDS OF NUCLEAR WEAPONS
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W87/Mk-21 Reentry Vehicles in storage, Warren Air Force Base, Cheyenne, Wyoming Photo courtesy of Paul Shambroom, www.paulshambroom.com
ARE CURRENTLY NON-DEPLOYED (i.e., IN RESERVE OR AWAITING DISMANTLEMENT)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
NUCLEAR WEAPONS HAVE UNIQUE SIGNATURES
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U.S. Scientists on a Soviet Cruiser in the Black Sea, 1989
BUT THEY ARE SENSITIVE AND CANNOT BE REVEALED TO INSPECTORS
Science, Vol. 248, 18 May 1990
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
NUCLEAR WARHEAD VERIFICATION
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KEY CONCEPTS OF (PROPOSED) SYSTEMS
ATTRIBUTE APPROACHConfirming selected characteristics
of an object in classified form (for example, the presence/mass of plutonium)
TEMPLATE APPROACHComparing the radiation signature
from the inspected item with a reference item (“golden warhead”) of the same type
INFORMATION BARRIERSTechnologies and procedures that
prevent the release of sensitive nuclear information (generally needed for both approaches)
edited by D. Spears, 2001
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PREVENTING THE EXCHANGE OF SENSITIVE INFORMATION DURING A RADIATION MEASUREMENT
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Trusted Information BarrierMeasure (but sanitize) sensitive information
Single-bit observation
“Hard” to authenticate and certify
Interactive Zero-knowledge ProofNever measure sensitive information
More complex observation
“Easy” to authenticate and certify
S. Philippe, B. Barak, and A. Glaser, “Designing Protocols for Nuclear Warhead Verification” 56th Annual INMM Meeting, July 12-16, 2015, Indian Wells, California
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
WHY ARE WARHEAD INSPECTIONS SO HARD?
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ADVERSARY/COMPETITOR HAS (DE FACTO) INFINITE RESOURCES
ADVERSARY/COMPETITOR MAY BE EXTREMELY MOTIVATED (TO DECEIVE INSPECTOR)Stakes are very high (especially when the number of weapons drops below ~1,000)
VERY LITTLE (IF ANY) INFORMATION ABOUT THE INSPECTED ITEM CAN BE REVEALEDSome information may be shared in advance, but no additional information during inspection
HOST HAS LAST OWNERSHIP OF INSPECTION SYSTEM BEFORE THE MEASUREMENT(and inspector never again has access to system aster the measurement is complete)
(AS SEEN FROM INSPECTOR’S PERSPECTIVE)
PASSIVE GAMMA SPECTROSCOPY WITH INFORMATION BARRIER
WHILE WE ARE WAITING
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
INFORMATION BARRIER EXPERIMENTAL
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VOLTAGE PULSES ACQUIRED BY THE RED PITAYA
Rejected pile-up
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
COMPARING RADIATION SPECTRA
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(IBX WITH SODIUM-IODIDE DETECTOR, 60 SECONDS, ~175,000 counts)
Template Inspected item
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
COMPARING RADIATION SPECTRA
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Differences are small, but most significant near 662 keV
(IBX WITH SODIUM-IODIDE DETECTOR, 60 SECONDS, ~175,000 counts)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
COMPARING RADIATION SPECTRA
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Co-60 source Co-60 source with weak Cs-137 contribution
(IBX WITH SODIUM-IODIDE DETECTOR, 60 SECONDS, ~175,000 counts)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PREVENTING THE EXCHANGE OF SENSITIVE INFORMATION DURING A RADIATION MEASUREMENT
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Trusted Information BarrierMeasure (but sanitize) sensitive information
Single-bit observation
“Hard” to authenticate and certify
Interactive Zero-knowledge ProofNever measure sensitive information
More complex observation
“Easy” to authenticate and certify
S. Philippe, B. Barak, and A. Glaser, “Designing Protocols for Nuclear Warhead Verification” 56th Annual INMM Meeting, July 12-16, 2015, Indian Wells, California
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PREVENTING THE EXCHANGE OF SENSITIVE INFORMATION DURING A RADIATION MEASUREMENT
18
Trusted Information BarrierMeasure (but sanitize) sensitive information
Single-bit observation
“Hard” to authenticate and certify
Interactive Zero-knowledge ProofNever measure sensitive information
More complex observation
“Easy” to authenticate and certify
S. Philippe, B. Barak, and A. Glaser, “Designing Protocols for Nuclear Warhead Verification” 56th Annual INMM Meeting, July 12-16, 2015, Indian Wells, California
INTERACTIVE ZERO-KNOWLEDGE PROOFSLOGICAL LAYER
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
INTERACTIVE ZERO-KNOWLEDGE PROOFS
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HUH?X
YES!
Q&A
P V
Zero-Knowledge Proofs: The prover (P) convinces the verifier (V) that s/he knows a secret without giving anything about the secret itself away
O. Goldreich, S. Micali, A. Wigderson, “How to Play ANY Mental Game,” 19th Annual ACM Conference on Theory of Computing, 1987 Graphics adapted from O. Goldreich, Foundations of Cryptography, Cambridge University Press, 2001; and eightbit.me
P V
YES!X
EXAMPLE
FOR AN “ILLUSTRATED PRIMER” ON ZERO-KNOWLEDGE PROOFS, SEE blog.cryptographyengineering.com/2014/11/zero-knowledge-proofs-illustrated-primer.html
FOR A ZERO-KNOWLEDGE “SUDOKU” PROOF, SEE www.wisdom.weizmann.ac.il/~naor/PAPERS/SUDOKU_DEMO/
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PROVING THAT TWO OBJECTS ARE IDENTICAL
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“THE DAY BEFORE THE INSPECTION”
1 2 3
A
B
(1) Alice owns valuable objects whose design she wants to keep a secret (2) In private, she takes a radiograph of this object on “blank film”
(3) Alice prepares two identical complements of that picture and places these complements in two sealed envelopes
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PROVING THAT TWO OBJECTS ARE IDENTICAL
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“THE DAY OF THE INSPECTION”
4 6
(4) At the day of the inspection, Alice presents a reference item and an item for inspection in concealed form (5) Bob randomly assigns the envelopes; then, new radiographs of both items are made
(6) If Alice presents a valid item, a “flat image” is produced; if not, she risks failing the inspection (and revealing information)
5
A/B
Reference item
Inspected item
Reference item
Inspected item (valid)
Source: ZDF.de (August 8,1985)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PROVING THAT TWO OBJECTS ARE IDENTICAL
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4 5 6
A/B
Reference item
Inspected item
Reference item
Inspected item (invalid)
(4) At the day of the inspection, Alice presents a reference item and an item for inspection in concealed form (5) Bob randomly assigns the envelopes; then, new radiographs of both items are made
(6) If Alice presents a valid item, a “flat image” is produced; if not, she risks failing the inspection (and revealing information)
“THE DAY OF THE INSPECTION”
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
PROVING THAT TWO OBJECTS ARE IDENTICAL
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+ =
=+
We will later introduce the maximum possible exposure as “NMAX”
“THE DAY OF THE INSPECTION”
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
COMPLETENESSIf the items are identical and both host and inspector follow the protocol,
then the inspector will accept with probability p = 1 – (½)n
WHAT THE PROTOCOL ACHIEVES
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ZERO KNOWLEDGEAs long as the host follows the protocol and presents matching items,
the inspector gains no knowledge during their interaction except for the fact that the items match
SOUNDNESSIf the items are different and the inspector follows the protocol,
then, no matter what the host does, the inspector will reject with probability p ≥ 1 – (½)n
S. Philippe, B. Barak, and A. Glaser, “Designing Protocols for Nuclear Warhead Verification” 56th Annual INMM Meeting, July 12-16, 2015, Indian Wells, California
PHYSICAL ZERO-KNOWLEDGE PROOFSWITH NON-ELECTRONIC PRELOADABLE DETECTORS
see, for example, B. Fisch, D. Freund, M. Naor, “Physical Zero-Knowledge Proofs of Physical Properties” Advances in Cryptology, CRYPTO 2014, Lecture Notes in Computer Science, Volume 8617, Springer, Heidelberg, 2014
THIS BASIC IDEA HAS TRIGGERED INTEREST IN OTHER “PHYSICAL APPLICATIONS” OF ZERO-KNOWLEDGE
14 MeV neutron generator (Thermo Scientific P 385)
Test object Detector array
Collimator
Collimator slot
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
SUPERHEATED DROPLET DETECTORS OFFER A WAY TO IMPLEMENT THIS PROTOCOL
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AND AVOID DETECTOR-SIDE ELECTRONICS
Superheated C-318 fluorocarbon (C4F8) droplets suspended in aqueous gel
Sensitive to neutrons with En > Emin
Tailor-made by d’Errico Research Group, Yale University
Designed to be insensitive to γ-radiation
Active volume .…...… : Droplet density …...… : Droplet diameter …… : Absolute Efficiency … :
6.0 cm3
3500 cm–3 ~100 µm
4 x 10–4
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
SUPERHEATED DROPLET DETECTORS
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Expanded bubble ~ 500 µm
Superheated droplet ~ 20–100 µm
Vapor microcavity (~ 0.1 µm) caused by ionizing radiation,
e.g. carbon or fluorine recoil ions in C4F8 droplets
PRINCIPLE
Aqueous gel with suspended
fluorocarbon droplets
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
FLUENCE RESPONSE
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Francesco d'Errico, “Radiation Dosimetry and Spectrometry with Superheated Emulsions” Nuclear Instruments and Methods in Physics Research B, 184 (2001), pp. 229–254
OF SUPERHEATED EMULSIONS MEASURED AS A FUNCTION OF NEUTRON ENERGY AND TEMPERATURE
40 ºC 35 ºC 30 ºC 25 ºC
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
SUPERHEATED DROPLET DETECTORS
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BUBBLES CAN BE COUNTED WITH A VARIETY OF TECHNIQUES
Detectors can be “reset” (bubbles recompressed) many times (good for R&D) Inspector can verify functionality of detectors aster inspection
Photodiodescollecting light scattered by bubbles
Diode output scales (quasi) linearly with bubble count
LEDs
Optical readout (with camera) Source: Bubble Technologies Industries
Opto-electronic readout Adapted from: Francesco d’Errico, Yale
Volumetric readout
RESULTSRADIOGRAPHY WITH 14-MeV NEUTRONS
(SIMULATED DATA)
14 MeV neutron generator (Thermo Scientific P 385)
Test object Detector array (preloaded)
Collimator
Collimator slot
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
ZERO-KNOWLEDGE VERIFICATION
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Reference item Valid item
RADIOGRAPHY WITH 14 MeV NEUTRONS
Simulated data from MCNP calculations; neutron detection energies > 10 MeV; N(max) = 5,000 A. Glaser, B. Barak, R. J. Goldston, “A Zero-knowledge Protocol for Nuclear Warhead Verification,” Nature, 510, 26 June 2014, 497–502
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
ZERO-KNOWLEDGE VERIFICATION
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Reference item Valid item
RADIOGRAPHY WITH 14 MeV NEUTRONS
Simulated data from MCNP calculations; neutron detection energies > 10 MeV; N(max) = 5,000 A. Glaser, B. Barak, R. J. Goldston, “A Zero-knowledge Protocol for Nuclear Warhead Verification,” Nature, 510, 26 June 2014, 497–502
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
ZERO-KNOWLEDGE VERIFICATION
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Simulated data from MCNP calculations; neutron detection energies > 10 MeV; N(max) = 5,000 A. Glaser, B. Barak, R. J. Goldston, “A Zero-knowledge Protocol for Nuclear Warhead Verification,” Nature, 510, 26 June 2014, 497–502
Valid item Invalid item
(Tungsten rings replaced by lead rings)
RADIOGRAPHY WITH 14 MeV NEUTRONS
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
LOCAL TUNGSTEN DIVERSION
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36-DEGREE SEGMENT OF OUTER TUNGSTEN RING (543 GRAMS, 7% OF TOTAL TUNGSTEN)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
ZERO-KNOWLEDGE VERIFICATION
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543 grams of tungsten removed from outer ring of test object; simulated data from MCNP calculations; neutron detection energies > 10 MeV A. Glaser, B. Barak, R. J. Goldston, “A Zero-knowledge Protocol for Nuclear Warhead Verification,” Nature, 510, 26 June 2014, 497–502
RADIOGRAPHY WITH 14 MeV NEUTRONS
The Conjurer, Hieronymus Bosch, 1502
FIRST EXPERIMENTAL RESULTS
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
EXPERIMENTAL SETUP AND SCENARIO
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WE WISH TO IDENTIFY CASES IN WHICH THE CUBE PATTERN HAS BEEN ALTERED WITHOUT GAINING ANY INFORMATION ABOUT THE CONFIGURATION IN CASES WHERE IT HAS NOT
SSAL
ALSS
AL
Staging area (with reference item)
Detector array
Collimated neutron beam 14-MeV (DT) generator
Reference item
SS
SSAL
ALAL
X
X X X
1 2 3 4 5 6 7Detector positions
Reference item consists of a combination of 2-inch cubes (aluminum and stainless steel)
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
EXPERIMENTAL RESULTS
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Bubb
le c
ount
400
600
800
1000
1200
1400
1600
NMAX = 1020
#1 #2 #3 #4 #5 #6 #7
Reference item
SS
SSAL
ALAL
X
X X X
(VALID ITEM)
Simulation Measurement
S. Philippe, R. J. Goldston, A. Glaser and F. d’Errico, “Experimental Demonstration of a Physical Zero-knowledge Protocol for Nuclear Warhead Verification,” under review
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
EXPERIMENTAL RESULTS
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Bubb
le c
ount
400
600
800
1000
1200
1400
1600
NMAX = 1020
#1 #2 #3 #4 #5 #6 #7
Reference item
SS
SSAL
ALAL
X
X X X
“Mirrored item”
AL
XAL
ALSS
SS
X X X
S. Philippe, R. J. Goldston, A. Glaser and F. d’Errico, “Experimental Demonstration of a Physical Zero-knowledge Protocol for Nuclear Warhead Verification,” under review
(A DRASTIC CHANGE)
Simulation Measurement
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
EXPERIMENTAL RESULTS
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Bubb
le c
ount
400
600
800
1000
1200
1400
1600
#1 #2 #3 #4 #5 #6 #7
Reference item
SS
SSAL
ALAL
X
X X X
“AL vs SS”
SS
ALAL
ALAL
X
X X X
(A SMALLER CHANGE)
Simulation Measurement
S. Philippe, R. J. Goldston, A. Glaser and F. d’Errico, “Experimental Demonstration of a Physical Zero-knowledge Protocol for Nuclear Warhead Verification,” under review
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
NEXT STEPS / WAY FORWARD
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AT LAB-SCALE: DEMONSTRATING ZERO-KNOWLEDGE APPROACHES
• Experimental reproducibility of results
• Two-color setting (e.g. 300 keV and 14 MeV neutrons)
• Maximize bubble loading (and confirm absence of bubble “aging”)
BEYOND LAB-SCALE: TOWARD FULL-SCALE INSPECTION SYSTEMS
• Leveraging the virtues of unclassified research Multidisciplinary, open for blue-sky ideas, involving international partners
• Experiments with special nuclear materials in real-world conditions Measurements at the Nevada National Security Site planned for … next week
Source: U.S. Department of Energy (bottom)
• Data commitment schemes
Photo: Mikhail Klimentyev/AP
A. Glaser, How to Keep a Secret, Technische Universität Darmstadt, 8. Juli 2016
ACKNOWLEDGEMENTSPRINCETON AND PPPL
Andrew Carpe Charles Gentile
Robert J. Goldston Sébastien Philippe
Yan Jie
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Boaz Barak, Microsost Research New England / Harvard University Francesco d’Errico, Yale University
Margarita Gattas-Sethi, Yale University Moritz Kütt, Technische Universität Darmstadt
ELSEWHERE
Global Zero MacArthur Foundation
Carnegie Corporation of New York U.S. Department of State
National Nuclear Security Administration, U.S. Department of Energy
RESEARCH SUPPORTED BY
Michael Schöppner Mark Walker
Bernadette Cogswell Julien de Troullioud de Lanversin
Tamara Patton
M. V. Ramana Zia Mian
Frank von Hippel Malte Göttsche
Benjamin Reimold