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.