Table Of Content

BREAK THE CODE Cryptography for Beginners kthecod rea tograph ryp Drb egin ner isn die nigs igoJ qyi (1q6 srIW be 6Si< Bud Johnson l^reak the (Zode Cryptography for Beginners 7§>uA Johnson IllustrationsbyLarryDaste DoverPublications, Inc. Mineola, NewYork — dedication Tomybeautifulwife,Evelyne—mylove,mypartner,withoutwhoseinsight, beliefandencouragementmycryptocareerwouldnothavehappened. ToM/Sgt.JimmyWest, who"awakened"metotheexcitementandcomplexitiesofcryptography. AndtothelovingmemoryofSgt.WilliamE.(Bill)Kelly,myArmyAirCorpsbuddy. Fromthejunglestothedesert,we'crypt'throughitall fromcryptographyschooltoalifelongfriendship,youmadeitablast,Kel. UC BR 7-About the 7Autkot J Bud Johnson served in World War II as a cryptographer/ joe cryptanalystfortheArmyAirCorps.Theactivitiesofhisand 1997 otheroverseas field intelligenceunits in the interception of enemy coded messages and the capture ofcodes and code equipment were important contributions to the successful NormandylandingsoftheAlliedinvasionforces,inJune1944, aswellastothewareffortingeneral. InJune1994,BudJohnson washonoredbytheFrenchgovernmentwithtwomedalsforhis wartimework. Copyright Copyright©1997byBudJohnson. All rightsreserved underPanAmerican and InternationalCopyright Conventions. PublishedinCanadabyGeneralPublishingCompany,Ltd.,30LesmillRoad, DonMills,Toronto,Ontario. PublishedintheUnitedKingdombyConstableandCompany,Ltd. BibliographicalNote BreaktheCode:CryptographyforBeginnersisanewwork,firstpublishedby DoverPublications,Inc.,in1997. LibraryofCongressCataloging-in-PublicalwnData Johnson,Bud. byBLraerarkytDhaestceo.de:cryptographyforbeginners/BudJohnson;illustrations p. cm. ISBN0-486-29146-4(pbk.) 1.Cryptography. I.Title. Z103.J65 1997 652'.8—dc21 97-19323 ManufacturedintheUnitedStatesofAmerica DoverPublications,Inc.,31East2ndStreet,Mineola,N.Y.11501 (Zontents Introduction iv "Crypto"Talk v Samplegridsheet vii Samplealphabetblanks viii SimpleLetterGrouping 2 SecretmessagesNos.1-8 TheReverseTrail 12 SecretmessagesNos.9-16 ShiftCode 22 SecretmessagesNos.17-25 MakeYourOwnSecretMessage KeyWordCode 34 SecretmessagesNos.26-34 MakeYourOwnSecretMessage DateShiftCode 46 SecretmessagesNos.35-43 MakeYourOwnSecretMessage TwistedPathCode 58 SecretmessagesNos.44-51 MakeYourOwnSecretMessage SolutionstotheSecretMessages 69 —— 3ntfiocLuctLon ENCOD INGAN DDECO DINGA RELOT SOFFU NWXYZ No,it'snotgibberish! Readletterbyletteruntilyoufindaword inthiscase,ENCODING. Keepgoingandyou'llfindthatthecoded messagereads: Encodinganddecodingarelotsoffun(wxyz) — — (Thosenonsenselettersattheend "wxyz" makethemessageeventrickiertoread!) — Younowknowonewaytodecode butcanyou. . . EGASS EMDED OCEHT KAERB It'seasy. JustreadthemessagebackwardstoBreakthecodedmessage. Almosteveryoneisintriguedbysecrets. Infact,overthecenturies — — manyfamouspeople andsomeinfamousones,too haveusedsecret methodsofwriting. Eventoday,governments,businessesandallsorts oforganizationsregularlyusecodestocommunicate. Inourbook,we'llintroduceyoutosomeofthetechniquesusedin thismysteriousglobalworldofcodes,ciphersandsecretwriting. You'll learnhoweachtechniqueworks. . .howtobreakthatkindofcode. . . andhowtousethattechniquetocreateyourownsecretmessages. Andyou'llhaveplentytosolvewithallthepracticemessagesscattered throughoutthesepages. Thecartoonsmayhelpyousolvethesecrets butiftheydon't,allofthesolutionsareprintedattheendofthebook. Havefun! Enjoy! 1[ereansometermscommonlyusedbyayptagrapheis BREAKINGACODE Discovering(learning)theintricaciesoftheformulathatsomeonehasusedto createacodeunknowntoyou. Theprocessofunravellingsuchacodecanbevery complex,andmayrequirebreakingscoresorhundredsoreventhousandsofcoded messagesbeforetheactualcodeitselfcanbebroken. BREAKINGAMESSAGE Theactoftranslatingamessagefromcodetocleartext. CLEARTEXTorINTHECLEARorPLAINTEXT Amessagewritteninplainlanguage,asopposedtoacodedorenciphered message. CODESand/orCIPHERS Thesetermsaresometimesusedinterchangeably. Technically,however, acoderequirestheuseofacodebook,orapre-selectedbookoraperiodical knownonlytothesenderandthereceiver; bothmusthavethecodekeybeing usedforamessage. Withoutthecodebookandcodekey,itisimpossibleto breakacodedmessage. Ciphersaremoreinteresting. Inacipher,eachplaintextletterischanged bysubstitutinganotherletterforit,orbytransposing(shifting)itinsomeway. Toavoidunnecessaryconfusioninterminology,thisbookusesthewords "code,""encoding"and"decoding"todescribeselectedtechniquesforsecret writing. CODEBOOK Abookcontainingwordsand/orsymbolsusedincodedmessages,together withtheiractual(plaintext)meaning. — — Wordsorsymbols sometimesbothusedincombination todenotethe typeofcodebeingused,alongwithoneormorekeyelementsofthecodeor cipher. Inthe"twistedpath"code,forexample(seepp.58-9),asamplecode keyis 5x6V T I i t J, R/L — containingallofthebasicinformationoneneedstobreakaspecificcoded message. "CRYPTO" Slang(amongfellowprofessionals)for"cryptographer"or"cryptanalyst." CRYPTOGRAPHY Theartandscienceofcreatingandbreakingcodesandciphers. DECODING Theprocessofchangingacodedmessagebackintoitsoriginalplaintextform. ENCODING Theprocessofchangingplaintextintocode. MONOALPHABETIC /POLYALPHABETIC Inamonoalphabeticsystem,onelettersubstitutesforoneandonlyoneletter. Inapolyalphabeticsystem,onelettermaystandinplaceofdifferentletterswithin thesamemessage. GARBLEorGARBLEDMESSAGE Anencodedmessagethathasbeenmessedupduetoerrorsinitstransmission orreception. Thetextmayskiponeormoreletters,lettergroupsand/orwhole sectionsofthemessage. NULL(S) Adummyornonsenseletterorgroupoflettersinsertedinamessage—usually atitsbeginningorend. Thepurposeofthenullistofilloutashort(incomplete) 5-letteror4-lettergroupinanencodedmessage. SUBSTITUTIONCIPHER Acodethatexchangesoneplaintextletterforanother. TRANSPOSITIONCIPHER Acodethatchangestheorderorsequenceoflettersintheplaintextmessage. ^Ready-made ^Alphabets fact Ski-fat and Key TOoid (Zodes A B C D E F G H I J K L M N O p Q R S T U V w X Y Z A B c D E F G H I J K L M N O p Q R s T u V w X Y Z A B c D E F G H I J K L M N o p Q R s T u V w X Y z A B c D E F G H I J K L M N o p Q R s T u V w X Y z A B c D E F G H I J K L M N o p Q R s T u V w X Y z A B c D E F G H I J K L M N o p Q R s T u V w X Y z A B c D E F G H I I K L M N o p Q R s T u V w X Y z A B c D E F G H I I K L M N p Q R s T u V w X Y z A B c D E F G H I J K L M N o p Q R s T u V w X Y z A B c D E F G H I J K L M N o p Q R s T u V vv X Y z A B c D E F G H I J K L M N o p Q R s T u V w X Y z