Steve Kent
The BBN security researcher who spent four decades writing the specifications for how the internet should protect itself — IPsec, PEM and secure BGP.
Kent earned his doctorate at MIT and spent most of his career at BBN, the firm that built the ARPANET's first routers. He was the principal author of Privacy Enhanced Mail in the early 1990s, an early attempt at encrypted email with a hierarchical PKI that never caught on but whose certificate model outlived it.
IPsec proved more durable: Kent wrote the architecture documents RFC 2401 (1998) and RFC 4301 (2005). He also led the work on S-BGP and later RPKI, meant to stop networks hijacking address space by announcing routes they don't own. That BGP hijacks still happen says more about deployment speed than about the design.