PURPLE: 7th Problem

Munitions Buildings, Washington D.C.

November 30, 1943

Dear young cryptanalysts,

A great misfortune has just happened: the Japanese
have changed the wiring of their Purple machine
used at the German Embassy. Perhaps this change
will be extended to all embassies.

Fortunately, we know Japanese phraseology very
well and we know many cribs. Your elders (Frank B.
Rolett, Robert O. Ferner, Genvieve Grotjan, Albert M.
Small) have succeeded in reconstructing the clear
text of a cryptogram coming from General Oshima.
There is only the last paragraph left to find.
Unfortunately your colleagues after two days of
nonstop work are exhausted and sleep soundly. You
have to make do with the texts I'm giving you.

You will be helped by the fact that the Japanese
have not changed their indicator system. Thanks to
the decoding of this one, here is the key of the
following message: motion: 123, Sixes: 1, Twenties:
1,19,1 and cipher mode.

We also know the SIXES by having analyzed all the
messages of the day (in alphabetical order): CDKMXZ

Good luck!

William F. Friedman

The beginning of the message in plain.

FROMZ GENER ALZHI ROSHI ZOSHI MAZTO ZTHEZ

MINIS TERZS TOPZG ENERA LZROM MELZM ADEZM

EZVIS ITZTH EZATL ANTIC ZWALL ZWHIC HZMUS

TZPUS HZOUR ZENEM IESZT OZSEA ZSTOP ZHERE

ZISZM YZREP ORTZO NZITS ZSTRU CTURE ZANDZ

ITSZR ESIST ANCEZ FORCE ZSTOP ZINZT OTALZ

COMMA ZMORE ZTHAN ZEIGH TZTHO USAND ZBUNK

ERSZH AVEZB EENZB UILTZ FORZT HEZAT LANTI

CZWAL LZSTO PZFOR ZEFFI CIENC YZREA SONSZ

COMMA ZSTAN DARDZ ORZRE GULAR ZBUIL DINGS

ZAREZ FITTE DZOUT ZFORZ THEZD IFFER ENTZB

RANCH ESZOF ZARMS ZCOMM AZMOS TZBUI LDING

SZARE ZBUIL TZACC ORDIN GZTOZ THESE ZPLAN

SZSTO PZTHE ZVARI OUSZB RANCH ESZOF ZTHEZ

ARMYZ COMMA ZAIRZ FORCE ZANDZ NAVYZ EACHZ

HAVEZ THEIR ZOWNZ EQUIP MENTZ COMMA ZMOST

ZOFZW HICHZ ISZST ANDAR DIZED ZSTOP ZTHEZ

TYPEZ OFZWE APONZ OFTEN ZREQU IRESZ THEZA

RMAME NTZOF ZINDI VIDUA LZINS TALLA TIONS

ZCOMM AZSOZ THEZW ZRZBU RGZRA DARZI SZOPE

RATED ZBYZT HEZAI RZFOR CEZCO MMAZE SPECI

ALLYZ HEAVY ZGUNZ BATTE RIESZ ANDZM ARINE

ZTARG ETZBA TTERI ESZAR EZOPE RATED ZBYZT

HEZNA VYZST OPZIN DIVID UALZS TANDA RDZBU

ILDIN GSZAR EZERE CTEDZ INZMO DULES ZCOMM

AZTHE IRZPR OTECT IVEZF UNCTI ONZAN DZTHE

IRZAR RANGE MENTZ ADAPT EDZTO ZTHEZ TOPOG

RAPHY ZSTOP ZFORZ EXAMP LEZCO MMAZM ARINE

ZTARG ETZBA TTERI ESZAR EZLOC ATEDZ NEARZ

THEZB EACHZ COMMA ZFIRE ZCONT ROLZP OSTSZ

AREZR AISED ZCOMM AZAND ZAMMU NITIO NZAND

ZCREW ZSYST EMSZA REZFU RTHER ZBACK ZSTOP

ZTHEZ INDIV IDUAL ZMODU LESZA REZCO NNECT

EDZEI THERZ BYZMO REZOR ZLESS ZFORT IFIED

ZTREN CHESZ ANDZP ARTLY ZBYZC OVERE DZPAT

HSZOR ZCAVI TIESZ STOPZ AZMAJ ORZDR AWBAC

KZOFZ THEZG ERMAN ZATLA NTICZ WALLZ ISZAB

OVEZA LLZTH EZSHA LLOWZ DEPTH ZOFZD EFENS

EZCOM MAZIN ZMANY ZPLAC ESZIT ZISZO NLYZA

ZFEWZ HUNDR EDZME TERSZ STOPZ IFZTH EZENG

LISHZ ANDZA MERIC ANSZC ROSSZ THEZF IRSTZ

LINEZ COMMA ZONLY ZLIGH TZSEL FZDEF ENSEZ

SYSTE MSZOF ZINFR ASTRU CTURE ZBUIL DINGS

ZEXIS TZINZ THEZI MMEDI ATEZH INTER LANDZ

COMMA ZOTHE RZLIN ESZHA VEZNO TZBEE NZPLA

NNEDZ PERMA NENTL YZSTO PZTHE REZIS ZNOZS

TRUCT UREZM ADEZU PZOFZ MANYZ INTER CONNE

CTEDZ LINES ZLIKE ZTHEZ MAGIN OTZLI NEZST

OPZAS ZAZRE SULTZ COMMA ZAFTE RZAZS UCCES

SFULZ BREAK THROU GHZIN ZTHEZ BEACH ZAREA

ZCOMM AZDEE PZPEN ETRAT IONZI NTOZT HEZHI

NTERL ANDZI SZPOS SIBLE ZSTOP

The cryptogram (without the indicator)

UVTXD BHPJS UUKJB SSIYS MVTJA DRZHT KQNQZ

MTWHT ORGKJ SIEDN PWSRE AXOVK MQGCD GKYKK

NXGVI RAZYF OXHOY YLLLZ KAYEE MESVZ HKKPT

YXSWY PZAHW KPITK FGSDG YKRAR KEFVY ZUAQS

KEGKK PXUIJ UQUCT HXGRB ZNUUR MATAG MTEMD

QLRCN QFFJU AEZHC EONCB MUEPQ KBQCT SRPUZ

XPMZG KMAOJ MUQEP KFJJN WXPOQ USNVX KJYRZ

UONDY OJJCV TJOXO EFUYC TQAKL JBCOF JPWJO

CXAVJ RZLTW IDHFQ MASTR MYYLC WXFHA LRVYC

MNZDJ MSNBE CEYKD BYDJU IWHAO KUBAT CSGVB

KLOWD IPLTE CZJGV KORFX ETEDC YTARR YUFXQ

PNIKH NYCUB MJVKB KMGXZ JXMHO LZOQA TKYHO

GXYHQ KTEYT FXOKC UHCQO NDGUX UGVYJ KGLLO

NXSOT UZQGN KTFUO BVTDY JEIMT ITDPR ZQRUC

EUZQX KIZKU KGFED WOOKN ZUHXC NWBPX WFKQD

VUBTD LQGNP ZOJIC UYEPU XJQSD MNKXB KDJLS

ZEOCW ONMNX TOCHN ANDFH XEDVM ZLUNB KJURX

YTVJD RIZEB TERJZ WJGQW KVPUL LOBID FALCW

PDOMI RAKUR KTRMP LNXOV UKFJI SJTGG TRPYL

KZPDK BXBYD AUHCW KYDAF JWKBH CLSKU QXJIA

UEAAM KBTXF NFKGJ YDIRU KFCXE DCQCH VBLKU

BRGWC WLRSW MNBOD HIQOA UNUIZ WTCCD VFPTV

MFVSU TAZNH GJGPQ RUKGS QDQBR RLPSC KJTCI

AWDTO SJKTI PBCQY CHOVC HYWCU HQYCL HDKQU

TYKUU OECIV UKPOH CSLCZ EPKZG CJWSF MKEKM

EKVHH NWDGY UWSKO LUSKP OVKPO OWZUR XXPHG

WTKIR TLPBO XFRPD QZJQY FKDWB ZHAQC REQQU

SNSFV KJRNS KEFJZ JKPZA LHCCS XDYDM SRWPS

KRSHF YYKWG VSFFT FNCSQ FKSUC SQLCZ FYRVC

RFRKT GVKGD MLKXS KRYFB ZXBFB EVYKO IAOPD

GFUCR GJOLM ZXTZD NDYWD MSZKN BQBFJ TXERM

ZXWGU KNUSQ NDNDG BYZRT JGVOO ZAAKK KIHRV

MAVED OODPO FKPSG ZMTXA BNPKG HSCXV TOEMW

HKDAR SPRJC UTCDN IHCYN KPSLR KULET FPFFX

KIHAE KTAVD BPDCT JPRWB ZBYCZ YUGOG CXPUB

SFZUE KZPNY QQLVC TYTAX FXZJJ OEZKE SQITC

KZNLC AUPKP FPZHS KUIWI WUUKZ UFSHC JVCEV

JERDS AOZAG EXJQV WUONC CNHVN MBPDC IRHVW

BXKQK MBKNN KMAII MHOSZ EUZSF KIVXA NYWCN

KQEOX HEOMS SZZXJ NNBLZ ORYPC PNCRS VXYPY

WYLYD FOXXQ MGYHZ EYBKC BVHOD TPPCJ YUBNZ

YQYJC MLZDQ MLYYI KIGUB IXSPT QZCVW PRWVX

IRJWH DVZVH KVVSS HOGPN MEWVI MIBQW CNTUP

KRCWI SZOAC SGJKG XDUMN FROCW NUWSJ PEHXC

MIZDH MTYGE HKRSB LRDYS WVKYF FDNPW EXTFF

GEYKD IAFMA HWHNN JDJNB LXWJQ APZGQ KOOXI

VERKR BNJKK IZJDV VKIVD MINLZ INQYE MVLYI

KWIMD YBLHN KQTDW ZISGC XQJFR QVCVN GAZLS

QWDER ZYKNA BAGTX KFZKR KYBRV TXFXQ PXZOF

NYORX YOWBK IVATS IVDAG ZUSVC LJHCT MIJQO

KMIXZ UXXTF IZILN FQLIH HWADU WHQCV PVDGQ

FITQO TFKKY AXITU NWVEA KTOOO ZNKZW CVCIH

VXIBM QTMCV TXRUZ VHKZI VWTUP MNOKM OBZQY

AXELY ZPTUT WNKKL GXNTZ BQUBD WXEWZ XUMZY

KNVTX RNCGR PGZWW IGDCP ZUJRS ARORQ WXHYD

LRKVM QXRBJ QVKYG BFUQX KHZKL KPRWL CEIIG

IZIHC FSSDV SZEDR VIVC