They is some extracts from a famous novel: CodedMessage.txt, which is encrypted using a simple substitution code e.g. “a/A” might stand for “m/M”; “b/B” might stand for “f/F” and The substitution is the same for the entire message.
This project tries to use MCMC(Markov chain Monte Carlo) method and reference table of pairwise letter frequency extracted from 7 novels in file LetterPairFreqFrom7Novels.txt to decode the coded message.
see the code details at code_cracking.Rmd
Gzo uclfg gcpo C qhcs okof te Gollk Qoeetb zo rhf slvem ce h LtqqfLtkio Fcqxol Rlhcgz tvgfcso gzo gollhio tu Gzo Sheiolf. Gzo ahlmced qtg hggoesheg zhs yltvdzg gzo ihl tvg hes zo rhf fgcqq ztqsced gzo sttl taoe yoihvfo Gollk Qoeetbf qoug uttg rhf fgcqq shedqced tvgfcso, hf cu zo zhs utldtggoe zo zhs teo. Zo zhs h ktvedqttmced uhio yvg zcf zhcl rhf yteo rzcgo. Ktv itvqs goqq yk zcf okof gzhg zo rhf aqhfgolos gt gzo zhclqceo, yvg tgzolrcfo zo qttmos qcmo hek tgzol ecio ktved dvk ce h sceeol jhimog rzt zhs yooe faoesced gtt pviz pteok ce h jtceg gzhg obcfgf utl gzhg avlatfo hes utl et tgzol. Gzolo rhf h dclq yofcso zcp. Zol zhcl rhf h qtxoqk fzhso tu shlm los hes fzo zhs h scfgheg fpcqo te zol qcaf hes txol zol fztvqsolf fzo zhs h yqvo pcem gzhg hqptfg phso gzo LtqqfLtkio qttm qcmo jvfg hetgzol hvgtptycqo. Cg scseg wvcgo. Etgzced ihe. Gzo hggoesheg rhf gzo vfvhq zhqugtvdz izhlhigol ce h rzcgo ithg rcgz gzo ehpo tu gzo lofghvlheg fgcgizos hiltff gzo ulteg tu cg ce los. Zo rhf doggced uos va. "Qttm, pcfgol," zo fhcs rcgz he osdo gt zcf xtcio, "rtvqs ktv pces h rztqo qtg avqqced ktvl qod cegt gzo ihl ft C ihe mces tu fzvg gzo sttl Tl fztvqs C taoe cg hqq gzo rhk ft ktv ihe uhqq tvg" Gzo dclq dhxo zcp h qttm rzciz tvdzg gt zhxo fgvim hg qohfg utvl ceizof tvg tu zcf yhim. Cg scseg ytgzol zcp oetvdz gt dcxo zcp gzo fzhmof. Hg Gzo Sheiolf gzok dog gzo ftlg tu aotaqo gzhg scfcqqvfcte ktv hytvg rzhg h qtg tu dtquced pteok ihe st utl gzo aolftehqcgk. H qtrfrved utlocde faoosfgol rcgz et gta slcugos cegt gzo ahlmced qtg hes h phe dtg tvg tu cg hes vfos gzo shfz qcdzgol te h qted icdhloggo. Zo rhf rohlced h avqqtxol izoim fzclg, koqqtr fqhimf, hes lcsced yttgf. Zo fgltqqos tuu glhcqced iqtvsf tu ceioefo, etg oxoe ytgzolced gt qttm gtrhlsf gzo LtqqfLtkio. Zo altyhyqk gztvdzg cg rhf itlek. Hg gzo uttg tu gzo fgoaf va gt gzo gollhio zo ahvfos gt fgcim h ptetiqo ce zcf oko. Gzo dclq fhcs rcgz h ecio yvlfg tu izhlp: "C zhxo h rtesoluvq csoh, shlqced. Rzk steg ro jvfg ghmo h ihy gt ktvl aqhio hes dog ktvl itexolgcyqo tvg Cgf fviz h rtesoluvq ecdzg utl h lve va gzo ithfg gt Ptegoicgt. C metr ftpo aotaqo gzolo rzt hlo gzltrced h sheio hltves gzo attq." Gzo rzcgozhclos qhs fhcs atqcgoqk: "Hruvqqk ftllk, yvg C steg zhxo cg hek ptlo. C rhf itpaoqqos gt foqq cg." Ultp zcf xtcio hes hlgcivqhgcte ktv rtvqseg zhxo metre zo zhs zhs hekgzced fgltedol gzhe tlhedo jvcio gt slcem. "Ftqs cg, shlqced Ztr st ktv pohe" Fzo fqcs hrhk ultp zcp hqted gzo fohg yvg zol xtcio fqcs hrhk h qtg uhlgzol gzhe gzhg. "C pohe C zhs gt," zo fhcs. "Utl ohgced pteok." "Tz, C foo." H fqcio tu favptec rtvqseg zhxo poqgos te zol etr. Gzo hggoesheg zhs gzo rzcgozhclos ytk lcdzg rzolo zo itvqs lohiz zcp ce h qtrceitpo ylhimog. "Qttm, yvfgol," zo fhcs, "Cxo dtg gt avg h ihl hrhk. Foo ktv ftpo ptlo ftpo tgzol gcpophkyo." Zo qog gzo sttl frced taoe. Gzo slvem altpagqk fqcs tuu gzo fohg hes qhesos te gzo yqhimgta te gzo fohg tu zcf ahegf. Ft C roeg txol hes sltaaos pk ecimoq. C dvoff cgf hqrhkf h pcfghmo gt cegoluolo rcgz h slvem. Oxoe cu zo metrf hes qcmof ktv zo cf hqrhkf qchyqo gt zhvq tuu hes atmo ktv ce gzo googz. C dtg zcp vesol gzo hlpf hes dtg zcp va te zcf uoog. "Gzhem ktv ft xolk pviz," zo fhcs atqcgoqk. Gzo dclq fqcs vesol gzo rzooq. "Zo dogf ft dtsshp Oedqcfz rzoe zof qthsos," fzo fhcs ce h fghceqofffgooq xtcio. "Gzhemf utl ihgizced zcp." "Cqq dog zcp ce gzo yhim tu gzo ihl," C fhcs. "Cp gollcyqk ftllk. Cp qhgo utl he oedhdopoeg." Fzo qog gzo iqvgiz ce hes gzo Ltqqf fghlgos gt dqcso. "Zof jvfg h qtfg std," fzo hssos rcgz h ittq fpcqo. "Aolzhaf ktv ihe uces h ztpo utl zcp. Zof ztvfoyltmoe ptlo tl qoff." Hes gzo Ltqqf gcimos stre gzo oeglheio slcxorhk tegt Fvefog Ytvqoxhls, phso h lcdzg gvle, hes rhf dteo. C rhf qttmced hugol zol rzoe gzo hggoesheg ihpo yhim. Hes C rhf fgcqq ztqsced gzo phe va hes zo rhf etr ftves hfqooa. "Roqq, gzhgf teo rhk tu stced cg," C gtqs gzo rzcgo ithg. "Fvlo," zo fhcs ikecihqqk. "Rzk rhfgo cg te h qvfz Gzop ivlxof hes hqq." "Ktv metr zcp" "C zohls gzo shpo ihqq zcp Gollk. Tgzolrcfo C steg metr zcp ultp h itrf ihyttfo. Yvg C teqk yooe zolo grt roomf." "Dog pk ihl, rcqq ktv" C dhxo zcp gzo gcimog. Yk gzo gcpo zo yltvdzg pk Tqsf txol C uoqg hf cu C rhf ztqsced va h fhim tu qohs. Gzo rzcgo ithg zoqaos po dog zcp cegt gzo ulteg fohg. Gzo ivfgtpol taoeos he oko hes gzhemos vf hes roeg gt fqooa hdhce. "Zof gzo atqcgofg slvem C oxol pog," C fhcs gt gzo rzcgo ithg. "Gzok itpo hqq fcnof hes fzhaof hes hqq mcesf tu pheeolf," zo fhcs. "Hes gzoklo hqq yvpf. Qttmf qcmo gzcf teo zhs h aqhfgci jty teo gcpo." "Kohz." C dhxo zcp h stqqhl hes zo gzhemos po. Zo rhf lcdzg hytvg gzo aqhfgci jty. Gzo lcdzg fcso tu pk eor ulcoesf uhio rhf ultnoe hes rzcgcfz hes fohpos rcgz gzce uceo fihlf. Gzo fmce zhs h dqtffk qttm hqted gzo fihlf. H aqhfgci jty hes h aloggk slhfgci teo. "Rzhgizh hcp gt st rcgz zcp" "Ghmo zcp ztpo hes ftyol zcp va oetvdz gt goqq po rzolo zo qcxof." Gzo rzcgo ithg dlceeos hg po. "Tmhk, fvimol. Cu cg rhf po, Cs jvfg slta zcp ce gzo dvggol hes mooa dtced. Gzop yttno ztvesf jvfg phmo h phe h qtg tu gltvyqo utl et uve. C dtg h azcqtftazk hytvg gzop gzcedf. Gzo rhk gzo itpaogcgcte cf etrhshkf h dvk zhf gt fhxo zcf fgloedgz gt altgoig zcffoqu ce gzo iqceizof." "C ihe foo ktvxo phso h ycd fviioff tvg tu cg," C fhcs. Zo qttmos avnnqos hes gzoe zo fghlgos gt dog phs, yvg yk gzhg gcpo C rhf ce gzo ihl hes ptxced. Zo rhf ahlgqk lcdzg tu itvlfo. Gollk Qoeetb phso po aqoegk tu gltvyqo. Yvg hugol hqq gzhgf pk qceo tu rtlm.
the first time i laid eyes on terry lennox he
was drunk in a rollsroyce silver wraith outside the terrace
of the dancers. the parking lot attendant had brought the
car out and he was still holding the door open
because terry lennoxs left foot was still dangling outside, as
if he had forgotten he had one. he had a
younglooking face but his hair was bone white. you could
tell by his eyes that he was plastered to the
hairline, but otherwise he looked like any other nice young
guy in a dinner jacket who had been spending too
much money in a joint that exists for that purpose
and for no other. there was a girl beside him.
her hair was a lovely shade of dark red and
she had a distant smile on her lips and over
her shoulders she had a blue mink that almost made
the rollsroyce look like just another automobile. it didnt quite.
nothing can. the attendant was the usual halftough character in
a white coat with the name of the restaurant stitched
across the front of it in red. he was getting
fed up. "look, mister," he said with an edge to
his voice, "would you mind a whole lot pulling your
leg into the car so i can kind of shut
the door or should i open it all the way
so you can fall out" the girl gave him a
look which ought to have stuck at least four inches
out of his back. it didnt bother him enough to
give him the shakes. at the dancers they get the
sort of people that disillusion you about what a lot
of golfing money can do for the personality. a lowswung
foreign speedster with no top drifted into the parking lot
and a man got out of it and used the
dash lighter on a long cigarette. he was wearing a
pullover check shirt, yellow slacks, and riding boots. he strolled
off trailing clouds of incense, not even bothering to look
towards the rollsroyce. he probably thought it was corny. at
the foot of the steps up to the terrace he
paused to stick a monocle in his eye. the girl
said with a nice burst of charm: "i have a
wonderful idea, darling. why dont we just take a cab
to your place and get your convertible out its such
a wonderful night for a run up the coast to
montecito. i know some people there who are throwing a
dance around the pool." the whitehaired lad said politely: "awfully
sorry, but i dont have it any more. i was
compelled to sell it." from his voice and articulation you
wouldnt have known he had had anything stronger than orange
juice to drink. "sold it, darling how do you mean"
she slid away from him along the seat but her
voice slid away a lot farther than that. "i mean
i had to," he said. "for eating money." "oh, i
see." a slice of spumoni wouldnt have melted on her
now. the attendant had the whitehaired boy right where he
could reach him in a lowincome bracket. "look, buster,"
he said, "ive got to put a car away. see
you some more some other timemaybe." he let the door
swing open. the drunk promptly slid off the seat and
landed on the blacktop on the seat of his pants.
so i went over and dropped my nickel. i guess
its always a mistake to interfere with a drunk. even
if he knows and likes you he is always liable
to haul off and poke you in the teeth. i
got him under the arms and got him up on
his feet. "thank you so very much," he said politely.
the girl slid under the wheel. "he gets so goddam
english when hes loaded," she said in a stainlesssteel voice.
"thanks for catching him." "ill get him in the back
of the car," i said. "im terribly sorry. im late
for an engagement." she let the clutch in and the
rolls started to glide. "hes just a lost dog," she
added with a cool smile. "perhaps you can find a
home for him. hes housebroken more or less." and
the rolls ticked down the entrance driveway onto sunset boulevard,
made a right turn, and was gone. i was looking
after her when the attendant came back. and i was
still holding the man up and he was now sound
asleep. "well, thats one way of doing it," i told
the white coat. "sure," he said cynically. "why waste
it on a lush them curves and all." "you know
him" "i heard the dame call him terry. otherwise i
dont know him from a cows caboose. but i only
been here two weeks." "get my car, will you" i
gave him the ticket. by the time he brought my
olds over i felt as if i was holding up
a sack of lead. the white coat helped me get
him into the front seat. the customer opened an eye
and thanked us and went to sleep again. "hes the
politest drunk i ever met," i said to the white
coat. "they come all sizes and shapes and all kinds
of manners," he said. "and theyre all bums. looks like
this one had a plastic job one time." "yeah." i
gave him a dollar and he thanked me. he was
right about the plastic job. the right side of my
new friends face was frozen and whitish and seamed with
thin fine scars. the skin had a glossy look along
the scars. a plastic job and a pretty drastic one.
"whatcha aim to do with him" "take him home and
sober him up enough to tell me where he lives."
the white coat grinned at me. "okay, sucker. if it
was me, id just drop him in the gutter and
keep going. them booze hounds just make a man a
lot of trouble for no fun. i got a philosophy
about them things. the way the competition is nowadays a
guy has to save his strength to protect hisself in
the clinches." "i can see youve made a big success
out of it," i said. he looked puzzled and then
he started to get mad, but by that time i
was in the car and moving. he was partly right
of course. terry lennox made me plenty of trouble. but
after all thats my line of work.