PURPLE: 3rd Problem

Munitions Buildings, Washington D.C.

September 30, 1940.

Dear Edward E. Christopher Jr.

We intercepted a new circular report encrypted
with the Purple machine that goes around the
embassies. It is urgent to decipher it. Fortunately,
we know the message key because we know the
meaning of almost all numeric indicators.

Each message is preceded by a numerical group of 5
digits. It corresponds to an indicator over-
encrypted by a number that changes every month.
We know this figure for the month: 34382.
The indicator is therefore: 04899 - 34382 = 70517. In
all there are 140 indicators. The indicator 70517
corresponds to the following key:

- Sixes switch start position: 21

- Twenties switches: start positions:

#1: 9, #2: 7, #3: 11

- Motion switch: 231

- Encryption mode

Cryptogram:

04899 KMHOJ SKEGS CBTMO STULT JOASD WADYZ

EJMCG DKAPW SFDKL KVGHG TNTAJ KVDPM HKOJE

ANRZY UDIMZ TZTZZ RSNDT AQQSV ATYAP UVEVA

KQVDL FOUOS ZDOXO YBPLS ADTGQ AORTJ LFAIV

ENOPO CNBPY JJOGB VFIZC CRNIN LDHSB HCXIR

NFQZX XEDIS XNBOB AYWZT XESZR LPDHL PIBRH

WZVET HXHVK DCHHA NNOLK RWZ

Good luck!

Frank B. Rolett,