Cipher Challenge
A Matter of Pairs
Playfair cipher. Standard Playfair transforms fixed pairs of letters rather than single letters. It uses a 5 × 5 square containing the alphabet with I and J sharing one position. Read the Ciphertext from its first letter as non-overlapping pairs: positions 1–2, 3–4, and so on. Pairs that cross those boundaries belong to a different analysis. To test a square, locate both letters of each pair. Letters in the same row move horizontally, letters in the same column move vertically, and letters at opposite corners of a rectangle take the other corners on their own rows. Decryption reverses the row and column movements; the rectangle rule is reciprocal. Cyclically shifting whole rows or columns can produce an equivalent working square, so recovering the constructor's exact visual arrangement is unnecessary. Classical analysis compares fixed-pair frequencies, repeated pair sequences, and reversed pairs with general English digraph patterns. Each proposed plaintext pair and ciphertext pair constrains how four letters can share rows, columns, or a rectangle; compatible proposals can gradually be combined into a square. Encryption may insert a null such as X or Q between repeated letters or at the end. A decrypted X or Q may therefore be either an ordinary letter or a filler, and that distinction must be interpreted from context.
Ciphertext
HAOCS LXQFC UHTUI ALXDS UMTNH ADHMO XSDMF GKIIP UNRZT XHPHN BLKIO PLPKE LCXDL GUTOP LPKEC GOPKB UHPDZ IGUPL FCPFV CPRNP LRXMH DQHFC XFCGG LSLSH KOHOS INSXL COELP FACPA AFZRO KCGGI CGHAX FFBLS POCBF BUCMK AFMSF VDMGF BCUMO PXBDH YFXBR CEIFC UOOQR OHAFB NCCIM YFCXL QPVYN XLXKV YFYFL XNHCB LXMSL XXEAQ PDLPY HKITU CGIDH BLFNO IKUNK ILPBF IACGH OBFNK EXDSL ONCYH FCHID XBESF BXLGT NLPHR QUOLX LSLSH KOLOY HFLUC AQLFL GHSIH TNIKH OMPIA GUPEL EBCYQ KOMPU NKITU QAFLU MXQCB LGPHF LBCXM OQDIA SUTHP MOTYF CZXCB CGBAN TLGUT HNBFH BIHRV DIKVB CNEUC CUGIK BUCCT XBUCR DKAGL OCNEP AELTU CBKIL DAFFS LGTAG IBCOG GIYQR APLHG NKXMH IDXPF ICIAI DZKMO SLFCR ZXCTU KMCNH AKMOG GITNL PEXAO DSPFF CARPT CFICO FPLHG YFCBG UPGAL SLCPE IGUIF GOLFP TOLNC KITUQ AFLUM XCCPY FXFPA UNRYC GUTHP GLABX BPQNH IAABL CFBXC TUKOU NTUZU KIUDC RKELF CUGIF LHAGU OLNCK IDFUZ PMHFX BUCUO OQLGM PELPF RAPLZ UESCG CUFSL GGNCB QGFQP TKILX EPPIA IYFIC OFPLU HFSUM PDUGX CTUCR UNXMU CRDIR CUGIL CDSKO FLUMC TSDBC GFWCB CPFDP ZILXM PNGFS RYHZI KULHQ NTLGF QCFZO FBUCP MIPOG GIARK VUTOQ KILOI SLXNK AFFQL EOCKO FBKIH PGUXB BFOPE LCPFL DHMOX LOCMK LXUQG QMKLO ZILGM PIATU BCUHF BCPZU OGMNP CMSKL CGTPQ EHUAL SFAOH SPAEI EFNZP IFBHB IHIAS DCNEL HPGUP HFCQH FCLGH AGUFS IEHWC GVSDS OCFBH PISZH WFPMX LEMNC YFPAA FOPKB UHPDU LBCOH FCIPY MCRHN HRALC GSLIP ULHQN TLGFS SXXBF CBCKI YFFEN PEIKI UFFCK MSNLP IANHP TFBGU GZIPL GELQG YSYFL CLCDS KOFLU MNCCP LCOQL XXLOG XLKOP ALPBF ZCUCD NUGSE PAEIH QZOLS RYKML DUTCP AQELB CHNKI FBZUX LLGRY CGUTH PGLCN FSBOL XDNGL PFFCR NSLPI DVARG LRYOL FYCOE LPFFC HRTIS LLYPH PDAIY DDKCO MPUNC RPEGU OEIAM PUZFB LCDSK OFLUM KIZBP MFMBC CBLCF BTUMO XQRCR LIAHQ DKPUF BHPYF FBXDL SDVFL UMDHY FLCLG NEPLA HIAEL QHKIZ COHIH OUSHK ITUQA FLUMR YPCCD BOCBF BQGYS HPULG UOBLX VDULP OFELS CIQXH NBFFS HAIKH OSIBC LOLPI AGFLS KNFLI PUHCG GITNL PHOCM PLKID XTUDN UHPDU LKBPA AFYFK NKIHP YFCBV HNCKI TUPMP UPDUG GIKIL DAFFS LGTAG IBCOG GIYFO KYHHD AQHPY FLGXB HANOC RGFSV CBKNL GHUSI MOCIC POTHZ MQKIU EHRSC SLDFC IGIIA RYCGU THPGL RZCUG LGLBA SFOLK IDXTU DNUHR CQGHU UZGLU CTVGQ MKEXD SNRCB FCHRN SBECB LXCBD XBEFG RCCGU GGPDL ALLCX DLGRY LGMOT QKOOZ FSHRZ ICBCU MPIAD OCBME VRFBK VYFPI CGEPL FIATU COMPI ACUGI UOOUC OUPCP MYLGT QIRLF RCLEI AMDBF UMXMH DCAKN YFGUS LSHAQ LXIPP FMOXE IAHQU CFPPI AIUQB CDXUM MOXEI CSLGN GSETC RHKLE DAIKN VUNYF CBGUD FDHMO LPHNN DUGMP IARCY FLEOC XBPMY RMOHA FCUPK AFBGO DMMDS ASMSP LXMPI AKIHP UOCOS HOLNC LCDSK OFLUM IAFGN HPAXL CZTIS LEFNG ZKPMF RKIRH NSOCO PLPIA YFSFR VXFLX DRXLW OCGXE LGFGC RTLMK AFMSF VDMGF BCUMV DLPMP IAXTS FYFLF KIOEI HKDGL TUFCO KOPXB LPUMV CIALD TIBCX CLPIA DHBFQ UYRFC UHTUI ALEIA TUQAS HFBOC FGSLS HKIUE FSBCP CHRDS YFUHO QLXLG FSOGX LOUCO FSOBZ RKIUF DCOHF CFXRY LGFCB FHIUL HQUHF BPMHP YFCBV HNCCP LOSFM VGLDN FYLCL GTAGI BCOGG IYFOK YHLDA FUQCO SHOLN COTPH DACOO TZXUC TUKMM IXBLG PAAFY FUHMO ETOKT ULCNH ISLXB CMKFB IAMKG LOBZR KIUEY FCGVS OUCOU PXCCT VRFBY FUHBF QUAHP AEIEF OQDIA SFBWF YFCBL SUHPD ULMOD QSFBX LGYQD HCNMP HNDFX SIADE FGRCX DOKUP NCBCN CPMFW LENHC GHGNK MKOCO TCOXL RYCGU THPGL AOBEN PSMNH OHMOG LYFUH HNBFO PTPNC DSCHS DMPIA PMXLE MYFLX GQDLS HDHGU LCDSK OFLUM LSLEH QOLPM FZZOC FKNGU PHFCQ CSFDH KIOPL PKELF PHPDU LHPFL UCAQC FSGXL OGCOV PIEHY AQIKU NNKWC CRQHD CCZNK GLYFS DUCCU DFDHG ULSLE HQOLN CIPXE AOBAC GGIBF ODFSV FCGQC HPKNO QDOKI UFLSF DCOOT OLXTT ULFLP GLDNF YLCLG TAGIB COGGI YFOKY HXLDX AMCGG IKVSC MKNHH DYFCB NDSCS EVCIR SDUHL GFSOG GLSLS HKOSH LSFDC OOTYF LDQOO CMUCB CTPVR ZLUPH NCRZT XCGXT QGMPM PDPGL OEVCI RLXOQ OHMPH OSNBA LGXHK VYFRY CGUTH PGLXL SVCBK NLGHU MLAIK XFBDF GLFBS LKITU QAFLU MCUSC CIBXV EIPTU GUHPD SCOHP QCHPX LSLSH SLYSF SQCGU OBNOX KZHMK GLEUZ OSFFC GLQXT XFSHN GLOCX MMDLS IDTGX LRYLG FSSLA BUOFT LXCUD FCTLS DSPFF CGZYF RCPMD LXEUH HAYFF GSLLD UNTNB OCBCB PDMAH UBXSC MKGLD NFYLC LGTAG IBCOG GIHDQ HHMPO SFFCQ PKEOL BCELP OFBGO COHNM PESLX CPIKU MFCTQ LCFBD HLSLE HQOLN CHRYL TNIKH OMPIA RYCGU THPGL HRUMK IGSPF VRRCR IGMUC FSQHC OULNK XCLPI AGZHP HNMPE XLGIP UNTPK FOCKI LEGRS LXCXT ALACI AVNFB ESRHQ LGUIP ULHQN TLGUT YFUHB CHRBO FBXDL GUTHP DRKOF GHDCR BOKIO CHVQE CBOZM PIAMO LUNHC GSXDR LENHC GYSHU HAFBH PYFXB FCUHT UIAFE KOBDC GSMAR ZNTCN HGSCM ZUFSC HACPL MPCFG OBFXE KOEFP FFCZU BFKCM VUNLO CHNPF SOCMK CBRYC GUTHP GLBCH RNUVN FBPMX PNCGS LCISN OGLIP UTPTC GGIFC SIFBU PKAYF CGWCC OUNLF LGMPU MROTU GUOGB OFLYF DIHDK HCGTP KOUNL SLEHQ OLNCB CLPTU GUELY FLCSD PLDIL XNPUT MOXEO CLCCB FCRZC PMYLG UHMOE QLXYQ FCUGU GQEHQ OHHQL SUHPD ULMOO SPAEI EFLFR DIPFB KIGUK ITUQA FLUMG UIVCN ELIPU MVCPH FCCAG UPEMO TQICO CESRH RIYEG FBCOG DFUMS LBCCZ TISLM KAFUT HOYSF SBCOG HCPCT UFCLQ HXOCK OLXUO UHFSK ADHVD CNKOA GMPIA BCCNF SPFPH FCTPU LVDLP MPIAK VYFTP PMGRS LDVMP HOSLS LFLUM CUAIQ ECBDX CHPAE ILXMP HNFSY FSFKN LCXDL GRYLG ESPAP EMOPF FCTPI KUTLS MYFCB FOPEL PDKIF BUGUP COSIM OCICP OTZXP MFYFC ISCGT PBCDH OHSLD XBOLF IATUC OMPIA PMBCD XNCFB RCBFK OULIH SFMOU NYFUH UODSO CFBIP YETGX LGUID BOKIO CHTAS AOTUF CTUCB CDXED VCBXD CGSLV EBFQU MOUIN OBCIV OLUPB CCUGI YFSFL SFDCO OTBCD XNCFB CNUNZ GDFKI HRUMC RSCSL BFSLS HKOHO MNPHP DULLE BCYQK OMPUN EFCIU NFBUG UPCOS CXMNH IAUFF CXLKI FSBCT UCULO OTCBN CCPUP KACUU ZULLC LGBCC NMPIA CTPVK IHPNH LEAOI KLTKI LDAFF SLGTA GIBCO GGIMD MYHMP ABRFC UHTUI AFBLX HCDKF BYFFB DNCOO TXTTU LFAIQ ZTPNC XMHOS CSLPF FCISZ HHGOK LOOTC BPMHP IRPME TNHKM ONKAN HFGCR NMHVU ICNHM NOBRA ROQIH PHFBY FLFSF AROBU HFCQH AOGMC RTYFC HNZKA RBFOP XLIPY SYFLX TXFST ICNEL OGBCP GELOG SIAOE FMPUG TSZGB CGUPF COULH DKHFB SLYSF SQCKI OUOKC UECHR BOKIU FPHFC OKVDL PMPIA LPUTQ ASLXQ CBLXK NISLC LGPAA FHDQO LGLOC NGIOU DSBKP UYFSD NOBCP EGQTU PMPUP DULBC LPTUF BYFLF PCHPW DPDPT AOKDU TDHLP UNSLS LYSFS COUGX MLPTU FCLOO TCBCT OCFBR YCGUT HPGLX EAOCO SHCBP LMPEX YHSLO HIHOU SHOTT XOLNC OCCOU NLFLG FULGC BUHFB EFAOO PRCHI BCKIH QOLUH SFAOI KUTUO DSOCG UELTP ZEDFT UFBRY CGUTH PGLEP XDOLL XBXBC IPDXQ CFEPU YFXFB XBCAI FPPLH RZLGL SHFBS AKOPC PMDLX CCPZU PFCOD XSCMK UNYFC RZNAO TUQAS HAQSF RVVPS HAQLX HRFKK IKIND UMDIS DYFSA WCBCU MRGCN ALFBO HCRXC CULOC HNPHU GISLY SFSQC HQGUE TRCFL PFACP AAFUC SPOCC GSCEI SDLGB FIDAK LSUHP DULMO QTYFU HHRNS BECGW CCOUN FBFST UFBGU IDQEC BDXOF CBSDC GFSIE HZLQF BARKV GMRCH NMPIA HIDXO GGIAR RZIKU LHQNT LGYTD NFYLC VDXLY FUHHI DXFLU MYFSB GSTUP DULHC PCXLP FFCHI BFKAR DBOCB EQSFB XLGXE DLALL CLGND GLCBK INFPT OLGUO EIHTN IKHOM PIAEF HOPTS FARXL RDBOC BLTUH FSBCI ELXTU RAKNY FGUYF SDFCA IFLUG YFLFX LXILX BCHRN UPMPD UGECS ATNCN FSVEP GKOUN MOXSD MSFKN CFFEL ENHCG GFSCC IRVMY FCCRH ZSXRH DLYHB CELPO FBARA IAQET CRNKU LMPUP MPIAL PGKKO HUKIG UOGKB ROOGG IRZLQ IKAFF SIPGL DNFYL CLGTA GIBCO GGILP SYFXD NFYFX YFPLA OKDUT BCHNK IFBYF PCCDH GIKZI LXMPN GHPBR ARNCR ZTXAO OGAIY FCBUO OUCOU PTUDP TICRD XFCIP FBKIO UKOLP GLDNF YLCLG TAGIB COGGI XLDXU MHMPO XBMOS LTUKM SLUNG NFBKV YFSPL XMPIA CURDP UFSSL ABUOF HMOTQ UOCBE QVCIR CUGIK ITUQA FLUME QLENH SDOCH PMYFC HRSCS LSHPD ULUHL KUNXE ICSLD FCIGI IAOQL XCBOP UNXDP ILGEL DHOHO CLCCB HRGIA SFSPF ACPAA FLQSF HALXF LHAGU PLTLH QONSX GUOBX DPLPD ULYFL FPCFS GIAQK INDHN DFDHR YCGUT HPGLP LAIYS MPFBH PIALD ZILGM PIAPM PLYFL DHNDF DHURN PSFLC DSKOF LUMCB ISOHK INGIP YEMDS ASMPI CGIAU HGRSL RYCBC DYFCB XEPAE IXLLD YQRCR NOUOK DHNKW CCRQC HNBFB FQUAO VSDSO CGRNC GUELO EOKSA PMHNB FBCLP TUGUE LFLUC AQGRS LUCSF DHGLF BSLXE OCKOF BRVBO EQXFI APFFC BCOHA RHGOD OLCGL TNCEK LSCIQ XNGDX RCBFB CIFPH PDUMR CLCFB CUGIU CSPOC CDMES FFSQC UPKAF BRCIP UGWHO QPCLD UMPCL EBCXH KICGH AHOXL YFCGV SOUCO UPLPZ IPMFB CPFLI ALCLS XLHPD SBHRC TYFCL CDSKO FLUMG UVEIP XEDOC BYFCF PIBFA KLSUH PDULM ODTRC YFLFX LXILX