Brian Snow

Snow spent 35 years at the NSA, mostly designing protected cryptosystems rather than breaking other people's. He became technical director of the Information Assurance Directorate, the part of the agency charged with protecting US government communications — a role that sometimes sat awkwardly with the offensive side's interests in the same building.

After retiring he became a widely quoted voice on assurance: the idea that a system needs not just the right security features but evidence that they hold up while someone is actively trying to make them fail. His 2005 essay "We Need Assurance!" is still a sharp critique of the industry's fondness for checklists.