Mahlon E. Doyle was an extraordinarily creative cryptomathematician whose accomplishments spanned a 31-year career at National Security Agency and its predecessor agencies. As an inventor, innovator, and author, Doyle profoundly affected the design of modern cryptographic devices.

His Communications Security (COMSEC) career began in 1949 as a cryptanalyst studying the new field of electronic key generators. Doyle was one of the pioneers in using mathematical notation to describe the motion of key generators and applying mathematical techniques to analyze them. He quickly established himself as the leading COMSEC cryptanalyst against electronic key generators when he discovered two general attack techniques that helped to lay the groundwork for significant SIGINT exploitations.

In 1956, Doyle joined the COMSEC Research and Development (R&D) organization as a cryptomathematician. By 1961, he had risen to Chief of the Cryptomathematics Division, a position he held until 1977, when he was named Senior Cryptographer in the COMSEC R&D Office. The division was responsible for designing the cryptographic algorithms used by the U.S. and its Allies to protect classified information and the U.S. Nuclear Command and Control System.

Doyle designed the cryptologics for major COMSEC systems that were used by the government for four decades. From the 1960s on, most U.S. government COMSEC equipment used cryptologics that were either designed by Doyle or designed by others based on his research.

Significant contributions to the design of COMSEC system architectures are also attributed to Doyle. He designed key management schemes that greatly enhanced the physical security of COMSEC devices and effected a dramatic decrease in the amount and cost of physically distributing key material.

Doyle was a prolific writer, publishing over 60 papers during his extended career. Most of the papers documented valuable advances to the cryptologic state of the art.

In recognition of his achievements, he received the NSA Exceptional Civilian Service Award in 1980. The citation praised his "invaluable contributions in advancing the state of the art of communications security at NSA."