Skip Site Navigation
HomeAbout UsCryptologic HeritageHistorical Figures and PublicationsHall of Honor

Hall of Honor

The Hall of Honor was created in 1999 to pay special tribute to the pioneers and heroes who rendered distinguished service to American cryptology.

The standards are high for induction into this great hall. The individuals honored were innovators over their entire careers or made major contributions to the structure and processes of American cryptology. The men and women who have been inducted to the Hall of Honor are all greats in the once silent world of cryptology.

In the early days of America's cryptologic effort, many of the "giants" did both Signals Intelligence and Information Assurance. They made important contributions to both offensive and defensive cryptology. As such, they were among the first inducted into the Hall of Honor.

Photos from the Hall of Honor may not be used without written permission of the National Security Agency, Public Affairs Office.

Leo Rosen

2010 Hall of Honor Inductee


Leo Rosen was instrumental in breaking the Japanese diplomatic code during World War II. His pioneering work in machine processing systems was the groundwork for much of the future U.S. excellence in cryptologic technology. He showed cryptologists the potential of processing equipment and helped the cryptologic services realize that potential in machine support in practical terms.

An ROTC graduate, Leo Rosen was called to active duty in 1939 with the Army Signal Intelligence Service (SIS). By the time he completed his cryptologic training, SIS workers had devised a "paper and pencil" method for solving one aspect of the Japanese machine cipher system known as "Purple."" The method was slow, cumbersome, and required many cryptanalysts.

Mr. Rosen prepared the layout of a machine that completely duplicated the function of the Japanese machine. With his equivalent, American cryptanalysts could simply type a "Purple" cipher text into a machine and retrieve a plain text decipherment from the printer. When the U.S. later recovered parts of an actual "Purple" machine, it was discovered that Japan, itself, had used stepping switches for their original device. Mr. Rosen had duplicated a machine he had never seen.

In 1940, Mr. Rosen was a member of a small team of Americans who made the initial cryptologic exchanges with the United Kingdom cryptologic organization. His technical knowledge contributed much then - and during the war years - to the good foundation for U.S.-UK technical collaboration in cryptology.

After the war, Mr. Rosen became Assistant Director of Research and chief engineer of the Army Security Agency, and later, for NSA. In 1967, NSA awarded him the Exceptional Civilian Service Award.