Adi Shamir
lorecryptographysecurity
The S in RSA, joint recipient of the 2002 Turing Award, and the author of the secret-sharing scheme that splits a key so that any k of n holders can reconstruct it.
The RSA work is what he is cited for, and the secret sharing may be the more widely deployed idea: it is how a root key can exist without any one person holding it, which is the arrangement used at the ceremonies that sign the DNS root. He also did foundational work on differential cryptanalysis, which is the other half of a cryptographer's job - the field advances as much by breaking constructions as by proposing them.
Also known as: shamir, secret sharing