Robert McEliece
The information theorist whose 1978 cryptosystem was ignored for forty years because the keys were too big — and then turned out to shrug off quantum computers.
McEliece (1942–2019) was a Caltech professor who worked on error-correcting codes for NASA's deep-space probes at JPL. In 1978, a year after RSA, he proposed a public-key scheme built on binary Goppa codes: the public key is a scrambled generator matrix, and encrypting means deliberately adding errors that only the key holder knows how to correct.
It was fast, but the public key ran to hundreds of kilobytes, which in the 1970s was absurd. The world picked RSA. Shor's algorithm then broke RSA on paper in 1994 and left McEliece standing, and Classic McEliece made the late rounds of NIST's post-quantum competition. He received the Claude E. Shannon Award in 2004 for his information-theory work, which is what he was actually known for.