Leo Rosen | |
|---|---|
 | |
| Born | 26 March 1916 |
| Died | 16 March 1991 (aged 74) |
| Nationality | American |
| Occupation | Cryptanalyst |
| Known for | Cryptanalysis of PURPLE |
Leo Rosen (26 March 1916 – 16 March 1991) was an Americancryptanalyst who worked withFrank Rowlett at Signals Intelligence Service (S.I.S.) before the start ofWorld War II onJapaneseciphers. Rowlett found a method to read the messages enciphered on the JapanesePURPLE machine. Rosen deduced correctly the mechanism of thecipher machine, even though the mechanism used by PURPLE, telephonestepping switches, was substantially different from other machines (such as thewired rotor andpinwheel machines).[1][additional citation(s) needed]
Rosen was born inWoodbine, New Jersey, to Joseph Rosen and Catherine Shubina, emigrants from the Russian Empire.[2]
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 Japaneseambassadors had themselves. Rosen also contributed hisengineering talents during and after the war atArlington Hall, after the S.I.S. became the Army Security Agency, later to become AFSA and finally the presentNational Security Agency.[1][additional citation(s) needed]
He died inArlington, Virginia, aged 71.[3]
In 2010, he was posthumously inducted into the NSA Hall of Honor for his contributions to the cryptology world.[1] He was represented by his son Lawrence Rosen and grandchildren Michael and Christine Rosen.
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