Carl Pomerance
American number theorist who invented the quadratic sieve, the method that broke RSA-129.
Pomerance (born 1944) introduced the quadratic sieve in 1981. It was the fastest general-purpose factoring method until the number field sieve arrived, and is still the best choice below roughly a hundred digits. In 1994 a variant of it factored RSA-129, the challenge Martin Gardner had said in 1977 would take 40 quadrillion years. It took eight months and 600 volunteers.
He has co-authored more papers with Paul Erdős than most people, and Prime Numbers: A Computational Perspective (2001, with Richard Crandall) is the standard reference for anyone who wants to understand why RSA keys have to be so long.