General Substitution Cryptograms

General Substitution Ciphers substitute one letter of the alphabet with another letter or symbol. For example, in a piece of text the word THE may be replaced by the word FSQ, where F represents T, and S represents H, and Q represents an E.

This will keep the message secret from prying eyes. However, this method of encryption has one fatal flaw. The message can still be broken, using a method known as frequency analysis. This involves analysing the ciphertext to see which letters appear most frequently in the text and deducing that they represent the most common letters in normal texts. The letters E, T then A appear most frequently in English texts, so the letters that appear most frequently in the encrypted text probably represent these.

You can find out more about Substitution Ciphers in the Black Chamber. There is also a section which will show you how to crack the Substitution Cipher for yourself, and it even includes a codebreaking tool.   

1. An Classic Tale About Vanity...

AKBP AKBP PSKFG KUC ZWJSQ KB SADSFCF LVC HVCIUVH GC AIOV CT BSL OZCHVSG HVKH VS GDSBH KZZ VWG ACBSP WB CFQSF HC CMHKWB HVSA VWG CBZP KAMWHWCB LKG HC MS KZLKPG LSZZ QFSGGSQ VS QWQ BCH OKFS TCF VWG GCZQWSFG KBQ HVS HVSKHFS QWQ BCH KAIGS VWA HVS CBZP HVWBU WB TKOH VS HVCIUVH KBPHVWBU CT LKG HC QFWJS CIH KBQ GVCL K BSL GIWH CT OZCHVSG VS VKQ K OCKH TCF SJSFP VCIF CT HVS QKP KBQ KG CBS LCIZQ GKP CT K YWBU VS WG WB VWG OKMWBSH GC CBS OCIZQ GKP CT VWA HVS SADSFCF WG WB VWG QFSGGWBU FCCA

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2. Two Famous Children's Authors

DROBO HGC YXKO EZYX G DSWO G PSCROBWGX VSFOM HSDR RSC HSPO SX G ZSQCDLO KVYCO IL DRO COG GXM OFOBL MGL RO HOXD YED PSCRSXQ GXM RO PSCROM GXM RO PSCROM GXM YXKO RO HGC CSDDSXQ HSDR RSC BYM VYYUSXQ GD DRO KVOGB HGDOB GXM RO CGD GXM RO CGD DROX RSC VSXO CEMMOXVL HOXD MYHX PGB MYHX IOVYH GXM HROX RO MBOH SD EZ GQGSX RO IBYEQRD YED G VGBQO PVYEXMOB DROX DRO PVYEXMOB CGSM DY RSW RGBU LYE PSCROBWGX S ZBGL LYE VOD WO VSFO S GW XY PVYEXMOB BOGVVL IED GX OXKRGXDOM ZBSXKO HRGD QYYM HSVV SD MY LYE DY USVV WO S CRYEVM XYD IO QYYM DY OGD ZED WO SX DRO HGDOB GQGSX GXM VOD WO QY KYWO CGSM DRO PSCROBWGX DROBO SC XY XOOM PYB CY WGXL HYBMC GIYED SD  G PSCR DRGD KGX DGVU S CRYEVM KOBDGSXVL VOD QY GXLRYH GXM HSDR DRGD RO ZED RSW IGKU GQGSX SXDY DRO KVOGB HGDOB GXM DRO PVYEXMOB HOXD DY DRO IYDDYW VOGFSXQ G VYXQ CDBOGU YP IVYYM IORSXM RSW DROX DRO PSCROBWGX QYD EZ GXM HOXD RYWO DY RSC HSPO SX DRO ZSQCDLO

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3. A Darwinian Piece..

SMWJ SW PZZD CZ CMW RJTRHRTGEPB ZY CMW BEXW HELRWCA ZL BGIHELRWCA ZY ZGL ZPTWL NGPCRHECWT VPEJCB EJT EJRXEPB ZJW ZY CMW YRLBC VZRJCB SMRNM BCLRDWB GB RB CMEC CMWA FWJWLEPPA TRYYWL XGNM XZLW YLZX WENM ZCMWL CMEJ TZ CMW RJTRHRTGEPB ZY EJA ZJW BVWNRWB ZL HELRWCA RJ E BCECW ZY JECGLW SMWJ SW LWYPWNC ZJ CMW HEBC TRHWLBRCA ZY CMW VPEJCB EJT EJRXEPB SMRNM MEHW IWWJ NGPCRHECWT EJT SMRNM MEHW HELRWT TGLRJF EPP EFWB GJTWL CMW XZBC TRYYWLWJC NPRXECWB EJT CLWECXWJC R CMRJD SW ELW TLRHWJ CZ NZJNPGTW CMEC CMRB FLWECWL HELREIRPRCA RB BRXVPA TGW CZ ZGL TZXWBCRN VLZTGNCRZJB MEHRJF IWWJ LERBWT GJTWL NZJTRCRZJB ZY PRYW JZC BZ GJRYZLX EB EJT BZXWSMEC TRYYWLWJC YLZX CMZBW CZ SMRNM CMW VELWJCBVWNRWB MEHW IWWJ WQVZBWT GJTWL JECGLW CMWLW RB EPBZ R CMRJD BZXW VLZIEIRPRCA RJ CMW HRWS VLZVZGJTWT IA EJTLWS DJRFMC CMEC CMRB HELREIRPRCA XEA IW VELCPA NZJJWNCWT SRCM WQNWBB ZY YZZT

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4. A Cryptogram With A Twist...

GPJDB, SB MDJTP, DOJ DQWP PO HTDOG UPDMJTOHW, D MDSST, DO DJNTMDQ OPGPMTPKW ZPM UTW QTOYW GP NDWPOMB, D GMTP PZ IDMJTODQW, D GMTP, GPP, PZ TOWTHOTZTIDOG VPQTGTITDOW (SPKHUG DOJ VDTJ ZPM SB D MTIU DOJ IPMMKVGDOHQP-IDODJTDO SDOYTOH IPMVPMDGTPO) TOZPMN KW DQQ PZ UPF PKM IPKOGMB OPF MTWYW JBTOH PZ WGDMXDGTPO.D MKNPKM, GUDGW NB TOTGTDQ GUPKHUG DW T WFTGIU PZZ NB MDJTP, MKNPKM PM VPWWTSQB D UPDL.

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Some letters may be substituted by more than one letter or symbol. For example, the letters A and B below, might both be substitutes for N.

IXDVMUFXLFEEFXSOQXYQVXSQTUIXWF*FMXYQVFJ*FXEFQUQX
JFPTUFXMX*ISSFLQTUQXMXRPQEUMXUMTUIXYFSSFI*MXKFJ
F*FMXLQXTIEUVFXEQTEFXSOQXLQ*XVFWMTQTUQXTITXKIJ*F
MUQXTQJMVX*QEYQVFQTHMXLFVQUVIXM*XEI*XLQ*XWITLIXE
QTHGXJQTUQXSITEFLQVGUQX*GXKIEUVGXEQWQTHGXDGUFXTIT
XDIEUQXGXKFKQVXSIWQXAVPUFXWGXYQVXEQJPFVXKFVUPUQXQX
SGTIESQTHGX*FXWFQFXSIWYGJTFXDQSFIXEFXGJPUFXSITXRPQEUG
XIVGHFITXYFSSFI*CXC*XSCWWFTIXSOQXCXYQTCXYIESFCX*FXCKV
QFXVFUQTPUFXQXKI*UCXTIEUVCXYIYYCXTQ*XWCUUFTIXLQFXVQW
FXDCSQWWIXC*FXC*XDI**QXKI*IXEQWYVQXCSRPFEUCTLIXLC*X*C
UIXWCTSFTIXUPUUQX*QXEUQ**QXJFCXLQX*C*UVIXYI*IXKQLQCX*CX
TIUUQXQX*XTIEUVIXUCTUIXACEEIXSOQXTITXEPVJQCXDPIVXLQ*X
WCVFTXEPI*IXSFTRPQXKI*UQXVCSSQEIXQXUCTUIXSCEEIX*IX*PWQ
XQVZXLFXEIUUIXLZX*ZX*PTZXYIFXSOQXTUVZUFXQVZKZWXTQX*Z*
UIXYZEEIRPZTLIXTZYYZVKQXPTZXWITUZJTZXAVPTZXYQVX*ZXLFEUZT
HZXQXYZVKQWFXZ*UZXUZTUIXRPZTUIXKQLPUZXTITXZKQZ
XZ*SPTZXTIFXSFXZ**QJVNWWIXQXUIEUIXUIVTIXFTXYFNTUIXS
OQXLQX*NXTIKNXUQVVNXPTXUPVAIXTNSRPQXQXYQVSIEE
QXLQ*X*QJTIXF*XYVFWIXSNTUIXUVQXKI*UQXF*XDQXJFVBVXSI
TXUPUUQX*BSRPQXBX*BXRPBVUBX*QKBVX*BXYIYYBXFTXEPEIXQX
*BXYVIVBXFVQXFTXJFPXSIWB*UVPFXYFBSRPQFTDFTXSOQX*XWBVXDP
XEIYVBXTIFXVFSOFPEIXX*BXYBVI*BXFTXSILFSQXQXQRPBUIV

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Please note that this final cipher is from stage 3 of the Cipher Challenge. Therefore I have not revealed the answer for this one. Happy cracking!

7. Oct 2002 ex-Competition Cipher

Type = General Monoalphabetic Substitution

ZRXGERMT OVWQ NA PJK THIJLB VS DYRFUC

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This competition is slightly different. Every book has an ISBN (International Standard Book Number), which is a code number used to identify the book.

Below is an ISBN that I have fabricated, perhaps to be used for a future book that I might write:

            1857028853

Unfortunately, the number is incorrect, because ISBNs must satisfy a strict mathematical criterion, engineered to help to spot errors. The ISBN is an example of an error-detecting code. Your challenge is to find out how ISBNs work and then fix the number above by changing the digit on the extreme right.

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