PURPLE: 4th Problem

Munitions Buildings, Washington D.C.

30 Octobre 1940

Dear Lawrence Clark,

Your mission is to try to find the key of two
messages encrypted with the Purple machine. The
Japanese made the mistake of sending the first
message in the plain first before the encrypted
version. You must properly decipher the second
message which has the same indicator (27916) and
which therefore has been encrypted with the same
key.

By analyzing the statistics of the messages of the
day, we found the letters that form the SIXES:
EJLMRZ

Good luck!

Frank B. Rolett,

1st message:

Plain text:

WEZHA VEZCH OSENZ TOZRE SPECT ZFREN CHZSO

VEREI GNTYZ INZIN DOCHI NAZST OPZEI THERZ

WAYZC OMMAZ WEZHA VEZTH EZPOW ERZST OPZTH

ATZIS ZWHAT ZMATT ERSZS TOPZO NZOCT OBERZ

FIVEZ WEZFR EEDZT HEZFR ENCHZ PRISO NERSZ

STOPZ WEZAL SOZLE AVEZT HEZAD MINIS TRATI

ONZOF ZTHEZ PROVI NCEZO FZLAN GZSON ZTOZT

HEZFR ENCHZ ADMIN ISTRA TIONZ STOPZ

Cryptogram:

BRENG NJEBF DBZFZ GBZRJ WTEII ZAMMF UQEXX

QMLRN IPKAZ UWRVT TYYBK PCEKP CARRY WTRRZ

VNXJW XMZKM GJEDC WMRDD JJDTN EZRBB KGEXT

YHEAS ESPGW MMWIT EZGJV VBCRQ SLWGG YQZJZ

NYXMZ TRRWR MRVRO AJEQL LUBUZ YLTIP XRJFE

GBBYM WJEGJ NORZL AVRLI DRRSK EAPPF AESYW

TDRAA MWXMZ WZQVG ICJRI PLRYV TLVKB MANLG

GRRNR MAHUM WTJKD IWDJU AGOIZ PQKKE

2st message (cryptogram):

VKEVI CQOEL EIGIG OFRLO PJZSE ORYMJ XZEHP

BWEUM DJMMY PEAJJ MDVST ELNRS MLKHM MZEKJ

JUJJQ NEDST NAEYX ETKRZ NLRVS TEJZU LRWMX

AONAB LTRUW VFZIS NQRRL DGWAL JJCFL LBVRA

MTSRZ NRESE LRAZL PLVOL EGGRZ LVNBZ OUGBI

WNQMK ALSQA TLWSM GOKEF LYBNE PZRGK VLTWM

BNRUF AZZXO JEPJC PDHRT TZRYS XEKUN UWZHA

VTRSD MLMMD RJKED XODXO JYZUF RQYZE KVBFW

JDWCZ ZYERH TJWHB TE