Roger Needham
British computer scientist (1935–2003) who laid the groundwork for how computers authenticate each other over an untrusted network.
The Needham–Schroeder protocol of 1978, written with Michael Schroeder, described how two parties can obtain a shared key through a trusted server. Its symmetric variant became the basis of Kerberos. Both variants later turned out to be flawed — Denning and Sacco found a replay attack in 1981, and Gavin Lowe broke the public-key version in 1995 — which became a lesson in itself about how hard protocols are.
That lesson led to BAN logic (1989, with Michael Burrows and Martín Abadi), a formal way to reason about what protocol participants are entitled to believe. With David Wheeler he designed the TEA block cipher in 1994. Needham was a professor at Cambridge and founded Microsoft Research Cambridge in 1997.