Cryptology Kasiski Analysis of a Polyalphabetically Encrypted Text

a7Hzq .#5r< kÜ\as TâÆK$ ûj(Ö2 ñw%h: Úk{4R f~`z8 ¤˜Æ+Ô „&¢Dø

      00    05    10    15    20    25    30    35    40    45

0000  AOWBK NLRMG EAMYC ZSFJO IYYVS HYQPY KSONE MDUKE MVEMP JBBOA
0050  YUHCB HZPYW MOOKQ VZEAH RMVVP JOWHR JRMWK MHCMM OHFSE GOWZK
0100  IKCRV LAQDX MWRMH XGTHX MXNBY RTAHJ UALRA PCOBJ TCYJA BBMDU
0150  HCQNY NGKLA WYNRJ BRVRZ IDXTV LPUEL AIMIK MKAQT MVBCB WVYUX
0200  KQXYZ NFPGL CHOSO NTMCM JPMLR JIKPO RBSIA OZZZC YPOBJ ZNNJP
0250  UBKCO WAHOO JUWOB CLQAW CYTKM HFPGL KMGKH AHTYG VKBSK LRVOQ
0300  VOEQW EALTM HKOBN CMVKO BJUPA XFAVK NKJAB VKNXX IJVOP YWMWQ
0350  MZRFB UEVYU ZOORB SIAOV VLNUK EMVYY VMSNT UHIWZ WSYPG KAAIY
0400  NQKLZ ZZMGK OYXAO KJBZV LAQZQ AIRMV UKVJO CUKCW YEALJ ZCVKJ
0450  GJOVV WMVCO ZZZPY WMWQM ZUKRE IWIPX BAHZV NHJSJ ZNSXP YHRMG
0500  KUOMY PUELA IZAMC AEWOD QCHEW OAQZQ OETHG ZHAWU NRIAA QYKWX
0550  EJVUF UZSBL RNYDX QZMNY AONYT AUDXA WYHUH OBOYN QJFVH SVGZH
0600  RVOFQ JISVZ JGJME VEHGD XSVKF UKXMV LXQEO NWYNK VOMWV YUZON
0650  JUPAX FANYN VJPOR BSIAO XIYYA JETJT FQKUZ ZZMGK UOMYK IZGAW
0700  KNRJP AIOFU KFAHV MVXKD BMDUK XOMYN KVOXH YPYWM WQMZU EOYVZ
0750  FUJAB YMGDV BGVZJ WNCWY VMHZO MOYVU WKYLR MDJPV JOCUK QELKM
0800  AJBOS YXQMC AQTYA SABBY ZICOB XMZUK POOUM HEAUE WQUDX TVZCG
0850  JJMVP MHJAB VZSUM CAQTY AJPRV ZINUO NYLMQ KLVHS VUKCW YPAQJ
0900  ABVLM GKUOM YKIZG AVLZU VIJVZ OGJMO WVAKH CUEYN MXPBQ YZVJP
0950  QHYVG JBORB SIAOZ HYZUV PASMF UKFOW QKIZG ASMMK ZAUEW YNJAB
1000  VWEYK GNVRM VUAAQ XQHXK GVZHU VIJOY ZPJBB OOQPE OBLKM DVONV
1050  KNUJA BBMDU HCQNY PQJBA HZMIB HWVTH UGCTV ZDIKG OWAMV GKBBK
1100  KMEAB HQISG ODHZY UWOBR ZJAJE TJTFU K

Repeated pattern    Index                  Difference

MDUHCQNY            147 1057               910 = 2·5·7·13
YWMWQMZ             345  464  737          119 = 7·17
                                           273 = 3·7·13
ZPYWM                56  462               406 = 2·7·29
UKEMV                37  373               336 = 2·2·2·2·3·7
PJBBO                44 1031               987 = 3·7·47
MDUK                 35  721               686 = 2·7·7·7
RMVU                427 1008               581 = 7·83
VLAQ                104  419               315 = 3·3·5·7
...

Because the text length excedes 1000 slightly, some of the repetitions of length 4 could be accidental, but almost sincerely none of length 5. The repetitions of lengths 7 and 8 are significant with extremely high probability.

This provides strong evidence for the encryption being periodic with period 7.