Jonathan Katz
American cryptographer best known as co-author of Katz–Lindell, the textbook that taught a generation to define security before claiming it.
Katz was for many years a professor at the University of Maryland. Introduction to Modern Cryptography, written with Yehuda Lindell and first published in 2007, swapped the older cookbook approach for formal definitions, explicit assumptions and reduction proofs. It became the standard university text and often sits next to Applied Cryptography on the shelf as its stricter sibling.
On the research side he is known for password-authenticated key exchange: with Rafail Ostrovsky and Moti Yung he gave, in 2001, one of the first efficient protocols proven secure in the standard model, with no random oracles. That line of work sits behind modern designs such as OPAQUE.