Leo Rosen
Encyclopedia
Leo Rosen was a U.S.
cryptanalyst who worked with Frank Rowlett
at Signals Intelligence Service (S.I.S.) before the start of World War II
on Japan
ese cipher
s. Rowlett found a method to read the messages enciphered on the Japanese PURPLE
machine. Rosen deduced correctly the mechanism of the cipher machine, even though the mechanism used by PURPLE was substantially different from other machines (such as the wired rotor and pinwheel
machines).
Rosen built a replica of PURPLE which turned out (when a machine was found years later) to use exactly the same telephone selector switches 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 had themselves. Rosen also contributed his engineering
talents during and after the war at Arlington Hall
, after the S.I.S. became the Army Security Agency, later to become AFSA and finally the present National Security Agency
.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
cryptanalyst who worked with Frank Rowlett
Frank Rowlett
Frank Byron Rowlett was an American cryptologist.Rowlett was born in Rose Hill, Virginia and attended Emory & Henry College in Emory, Virginia, where he was a member of the Beta Lambda Zeta fraternity. In 1929 he received a bachelor's degree in mathematics and chemistry...
at Signals Intelligence Service (S.I.S.) before the start of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
on Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese cipher
Cipher
In cryptography, a cipher 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. In non-technical usage, a “cipher” is the same thing as a “code”; however, the concepts...
s. Rowlett found a method to read the messages enciphered on the Japanese PURPLE
PURPLE
In the history of cryptography, 97-shiki ōbun inji-ki or Angōki Taipu-B , codenamed Purple by the United States, was a diplomatic cryptographic machine used by the Japanese Foreign Office just before and during World War II...
machine. Rosen deduced correctly the mechanism of the cipher machine, even though the mechanism used by PURPLE was substantially different from other machines (such as the wired rotor and pinwheel
Pinwheel (cryptography)
In cryptography, a pinwheel was a device for producing a short pseudorandom sequence of bits , as a component in a cipher machine. A pinwheel consisted of a rotating wheel with a certain number of positions on its periphery. Each position had a "pin" or "lug" which could be either "set" or "unset"...
machines).
Rosen built a replica of PURPLE which turned out (when a machine was found years later) to use exactly the same telephone selector switches 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 had themselves. Rosen also contributed his engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
talents during and after the war at Arlington Hall
Arlington Hall
Arlington Hall was a former girl's school and the headquarters of the US Army's Signal Intelligence Service cryptography effort during World War II. The site presently houses the George P. Shultz National Foreign Affairs Training Center, and the United States National Guard Readiness Center. It...
, after the S.I.S. became the Army Security Agency, later to become AFSA and finally the present National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
.