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.
Source & status
- Origin
- Original to Decipher
- Solution
- Established
Ciphertext
HA OC SL XQ FC UH TU IA LX DS UM TN HA DH MO XS DM FG KI IP UN RZ TX HP HN BL KI OP LP KE LC XD LG UT OP LP KE CG OP KB UH PD ZI GU PL FC PF VC PR NP LR XM HD QH FC XF CG GL SL SH KO HO SI NS XL CO EL PF AC PA AF ZR OK CG GI CG HA XF FB LS PO CB FB UC MK AF MS FV DM GF BC UM OP XB DH YF XB RC EI FC UO OQ RO HA FB NC CI MY FC XL QP VY NX LX KV YF YF LX NH CB LX MS LX XE AQ PD LP YH KI TU CG ID HB LF NO IK UN KI LP BF IA CG HO BF NK EX DS LO NC YH FC HI DX BE SF BX LG TN LP HR QU OL XL SL SH KO LO YH FL UC AQ LF LG HS IH TN IK HO MP IA GU PE LE BC YQ KO MP UN KI TU QA FL UM XQ CB LG PH FL BC XM OQ DI AS UT HP MO TY FC ZX CB CG BA NT LG UT HN BF HB IH RV DI KV BC NE UC CU GI KB UC CT XB UC RD KA GL OC NE PA EL TU CB KI LD AF FS LG TA GI BC OG GI YQ RA PL HG NK XM HI DX PF IC IA ID ZK MO SL FC RZ XC TU KM CN HA KM OG GI TN LP EX AO DS PF FC AR PT CF IC OF PL HG YF CB GU PG AL SL CP EI GU IF GO LF PT OL NC KI TU QA FL UM XC CP YF XF PA UN RY CG UT HP GL AB XB PQ NH IA AB LC FB XC TU KO UN TU ZU KI UD CR KE LF CU GI FL HA GU OL NC KI DF UZ PM HF XB UC UO OQ LG MP EL PF RA PL ZU ES CG CU FS LG GN CB QG FQ PT KI LX EP PI AI YF IC OF PL UH FS UM PD UG XC TU CR UN XM UC RD IR CU GI LC DS KO FL UM CT SD BC GF WC BC PF DP ZI LX MP NG FS RY HZ IK UL HQ NT LG FQ CF ZO FB UC PM IP OG GI AR KV UT OQ KI LO IS LX NK AF FQ LE OC KO FB KI HP GU XB BF OP EL CP FL DH MO XL OC MK LX UQ GQ MK LO ZI LG MP IA TU BC UH FB CP ZU OG MN PC MS KL CG TP QE HU AL SF AO HS PA EI EF NZ PI FB HB IH IA SD CN EL HP GU PH FC QH FC LG HA GU FS IE HW CG VS DS OC FB HP IS ZH WF PM XL EM NC YF PA AF OP KB UH PD UL BC OH FC IP YM CR HN HR AL CG SL IP UL HQ NT LG FS SX XB FC BC KI YF FE NP EI KI UF FC KM SN LP IA NH PT FB GU GZ IP LG EL QG YS YF LC LC DS KO FL UM NC CP LC OQ LX XL OG XL KO PA LP BF ZC UC DN UG SE PA EI HQ ZO LS RY KM LD UT CP AQ EL BC HN KI FB ZU XL LG RY CG UT HP GL CN FS BO LX DN GL PF FC RN SL PI DV AR GL RY OL FY CO EL PF FC HR TI SL LY PH PD AI YD DK CO MP UN CR PE GU OE IA MP UZ FB LC DS KO FL UM KI ZB PM FM BC CB LC FB TU MO XQ RC RL IA HQ DK PU FB HP YF FB XD LS DV FL UM DH YF LC LG NE PL AH IA EL QH KI ZC OH IH OU SH KI TU QA FL UM RY PC CD BO CB FB QG YS HP UL GU OB LX VD UL PO FE LS CI QX HN BF FS HA IK HO SI BC LO LP IA GF LS KN FL IP UH CG GI TN LP HO CM PL KI DX TU DN UH PD UL KB PA AF YF KN KI HP YF CB VH NC KI TU PM PU PD UG GI KI LD AF FS LG TA GI BC OG GI YF OK YH HD AQ HP YF LG XB HA NO CR GF SV CB KN LG HU SI MO CI CP OT HZ MQ KI UE HR SC SL DF CI GI IA RY CG UT HP GL RZ CU GL GL BA SF OL KI DX TU DN UH RC QG HU UZ GL UC TV GQ MK EX DS NR CB FC HR NS BE CB LX CB DX BE FG RC CG UG GP DL AL LC XD LG RY LG MO TQ KO OZ FS HR ZI CB CU MP IA DO CB ME VR FB KV YF PI CG EP LF IA TU CO MP IA CU GI UO OU CO UP CP MY LG TQ IR LF RC LE IA MD BF UM XM HD CA KN YF GU SL SH AQ LX IP PF MO XE IA HQ UC FP PI AI UQ BC DX UM MO XE IC SL GN GS ET CR HK LE DA IK NV UN YF CB GU DF DH MO LP HN ND UG MP IA RC YF LE OC XB PM YR MO HA FC UP KA FB GO DM MD SA SM SP LX MP IA KI 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