Leo Rosen was a

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

cryptanalyst Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic sec ...

who worked with

Frank Rowlett Frank Byron Rowlett (May 2, 1908 – June 29, 1998) was an American cryptologist. Life and career Rowlett was born in Rose Hill, Lee County, Virginia and attended Emory & Henry College in Emory, Virginia. In 1929 he received a bachelor's d ...

at Signals Intelligence Service (S.I.S.) before the start of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

ese

cipher In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is ''encipherment''. To encipher or encode i ...

s. Rowlett found a method to read the messages enciphered on the Japanese

PURPLE Purple is any of a variety of colors with hue between red and blue. In the RGB color model used in computer and television screens, purples are produced by mixing red and blue light. In the RYB color model historically used by painters, pu ...

machine. Rosen deduced correctly the mechanism of the

cipher machine In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is ''encipherment''. To encipher or encode i ...

, even though the mechanism used by PURPLE, telephone

stepping switch In electrical control engineering, a stepping switch or stepping relay, also known as a uniselector, is an electromechanical device that switches an input signal path to one of several possible output paths, directed by a train of electrical pulse ...

es, was substantially different from other machines (such as the wired rotor and pinwheel machines). WE 206A stepping switch front

Rosen built a replica of PURPLE which turned out (when a machine was found years later) to use stepping switches similar to those in common use at that time in the U.S. This machine was used to decode the Japanese diplomatic messages, sometimes before the Japanese

ambassadors An ambassador is an official envoy, especially a high-ranking diplomat who represents a state and is usually accredited to another sovereign state or to an international organization as the resident representative of their own government or so ...

had themselves. Rosen also contributed his

engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

talents during and after the war at

Arlington Hall Arlington Hall (also called Arlington Hall Station) is a historic building in Arlington, Virginia, originally a girls' school and later the headquarters of the United States Army's Signal Intelligence Service (SIS) cryptography effort during Wor ...

, after the S.I.S. became the Army Security Agency, later to become AFSA and finally the present

National Security Agency The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collecti ...

. In 2010 he was posthumestly inducted into the NSA Hall of Honor for his contributions to the cryptology world. He was represented by his son Lawrence Rosen and favorite grandson, Michael Rosen with dat BDE, grand daughter Christine Rosen, and Baby deyuck the real felipo the human dilipdo Rosen.

References

National Security Agency cryptographers Year of birth missing Year of death missing Signals Intelligence Service cryptographers {{US-scientist-stub

See also

References