Whitfield Diffie is a consulting scholar at CISAC. He was a visiting scholar in 2009-2010 and an affiliate from 2010-2012. He is best known for the discovery of the concept of public key cryptography, in 1975, which he developed along with Stanford University Electrical Engineering Professor Martin Hellman. Public key cryptography, which revolutionized not only cryptography but also the cryptographic community, now underlies the security of internet commerce.

During the 1980s, Diffie served as manager of secure systems research at Northern Telecom. In 1991, he joined Sun Microsystems as distinguished engineer and remained as Sun fellow and chief security officer until the spring of 2009.

Diffie spent the 1990s working to protect the individual and business right to use encryption, for which he argues in the book Privacy on the Line, the Politics of Wiretapping and Encryption, which he wrote jointly with Susan Landau. Diffie is a Marconi fellow and the recipient of a number of awards including the National Computer Systems Security Award (given jointly by NIST and NSA) and the Franklin Institute's Levy Prize.

Paul K. MacDonald is a doctoral candidate at Columbia University and a 2004-2005 predoctoral fellow at CISAC. His research focuses on how great powers utilize the institution of imperial rule in order to exert control over less powerful polities in the international system. Most recently, he has published research on the epistemological foundations of rational choice theory in the American Political Science Review and on the relevance of evolutionary biology to international politics in International Security.

Scott D. Sagan is Co-Director and Senior Fellow at the Center for International Security and Cooperation, the Caroline S.G. Munro Professor of Political Science, and the Bass University Fellow in Undergraduate Education at Stanford University. He also serves as Co-Chair of the American Academy of Arts and Sciences’ Committee on International Security Studies. Before joining the Stanford faculty, Sagan was a lecturer in the Department of Government at Harvard University and served as special assistant to the director of the Organization of the Joint Chiefs of Staff in the Pentagon.

Sagan is the author of Moving Targets: Nuclear Strategy and National Security (Princeton University Press, 1989); The Limits of Safety: Organizations, Accidents, and Nuclear Weapons (Princeton University Press, 1993); and, with co-author Kenneth N. Waltz, The Spread of Nuclear Weapons: An Enduring Debate (W.W. Norton, 2012). He is the co-editor of Insider Threats (Cornell University Press, 2017) with Matthew Bunn; and co-editor of The Fragile Balance of Terror (Cornell University Press, 2022) with Vipin Narang. Sagan was also the guest editor of a two-volume special issue of Daedalus: Ethics, Technology, and War (Fall 2016) and The Changing Rules of War (Winter 2017).

Recent publications include “Creeds and Contestation: How US Nuclear and Legal Doctrine Influence Each Other,” with Janina Dill, in a special issue of Security Studies (December 2025); “Kettles of Hawks: Public Opinion on the Nuclear Taboo and Noncombatant Immunity in the United States, United Kingdom, France, and Israel”, with Janina Dill and Benjamin A. Valentino in Security Studies (February 2022); “The Rule of Law and the Role of Strategy in U.S. Nuclear Doctrine” with Allen S. Weiner in International Security (Spring 2021); “Does the Noncombatant Immunity Norm Have Stopping Power?” with Benjamin A. Valentino in International Security (Fall 2020); and “Just War and Unjust Soldiers: American Public Opinion on the Moral Equality of Combatants” and “On Reciprocity, Revenge, and Replication: A Rejoinder to Walzer, McMahan, and Keohane” with Benjamin A. Valentino in Ethics & International Affairs (Winter 2019).

In 2022, Sagan was awarded Thérèse Delpech Memorial Award from the Carnegie Endowment for International Peace at their International Nuclear Policy Conference. In 2017, he received the International Studies Association’s Susan Strange Award which recognizes the scholar whose “singular intellect, assertiveness, and insight most challenge conventional wisdom and intellectual and organizational complacency" in the international studies community. Sagan was also the recipient of the National Academy of Sciences William and Katherine Estes Award in 2015, for his work addressing the risks of nuclear weapons and the causes of nuclear proliferation. The award, which is granted triennially, recognizes “research in any field of cognitive or behavioral science that advances understanding of issues relating to the risk of nuclear war.” In 2013, Sagan received the International Studies Association's International Security Studies Section Distinguished Scholar Award. He has also won four teaching awards: Stanford’s 1998-99 Dean’s Award for Distinguished Teaching; Stanford's 1996 Hoagland Prize for Undergraduate Teaching; the International Studies Association’s 2008 Innovative Teaching Award; and the Monterey Institute for International Studies’ Nonproliferation Education Award in 2009.