len adlmen · CC BY-SA 3.0

The A in RSA. In 1977, with Ron Rivest and Adi Shamir, he worked out how to make public-key cryptography practical rather than merely theoretical — the reason two strangers can agree on a secret over an open line, and the basis of most encryption in use today. Also founded the field of DNA computing, showing in 1994 that a test tube of DNA strands could solve a small instance of the travelling salesman problem. Born to a Jewish family in California whose own family had immigrated from the Minsk area of modern-day Belarus.