Leo Rosen

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

[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.

Rosen also contributed his engineering talents during and after the war at Arlington Hall, after the S.I.S.

[1][additional citation(s) needed] He died in Arlington, Virginia, aged 71.

[3] In 2010, he was posthumously inducted into the NSA Hall of Honor for his contributions to the cryptology world.

Stepping switch of the type used by Rosen to build an analog of the PURPLE machine
Fragment of a Japanese PURPLE machine recovered after the war. The Japanese used three 7-layer switches for each stage of the cipher; Rosen used four 6-layer switches per stage. Cryptographically, there was no difference.