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03. [50p] Solving a substitution cipher

Time to get your hands dirty! Below, you have a ciphertext. Specifically, this output is the result of a substitution cipher, meaning that every letter in the English alphabet has been assigned a random, unique correspondent. As you may have noticed, digits and special characters remain unchanged.

Your task is to write a Python script that will help you break the cipher and decode the original text.

use a dictionary to map each encoded character back to it's original value
populate this dictionary as you progress in your attempt
whenever you run the script, it should print the text to the screen, with a few minor changes:
- any character that exists as a key in the dictionary should be replaced with what you think the correspondent is.
- any replaced character should be highlighted in bold red.

Click to display ⇲

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uncrackable.txt

MIT YSAU OL OYGFSBDGRTKFEKBHMGCALSOQTMIOL. UTFTKAMTR ZB DAKQGX EIAOF GY MIT 
COQOHTROA HAUT GF EASXOF AFR IGZZTL. ZT CTKT SGFU, MIT YSACL GF A 2005 HKTLTFM 
MODTL MIAF LMADOFA GK A CTTQSB LWFRAB, RTETDZTK 21, 1989 1990, MIT RKTC TROMGKL 
CAL WHKGGMTR TXTKB CGKSR EAF ZT YGWFR MIT EGFMOFWTR MG CGKQ AM A YAOMIYWS 
KTHSOTL CITKT IGZZTL, LMBST AOD EASXOF, AMMAEQ ZGMI LORTL MG DAKQL, "CIAM RG 
EGFMKGSSOFU AF AEMWAS ZGAKR ZGVTL OF MIT HKTHAKTFML FADT, OL ODHWSLOXT KADHAUTL 
OF CIOEI ASCABL KTYTKTFETL MIT HALLCGKR, CIOEI DGFTB, AFR MITB IAR SOMMST YKGFM 
BAKR IOL YKWLMKAMTR EGSGK WFOJWT AZOSOMB COMI AFR OFROLHTFLAMT YGK MTAEI GMITK 
LMWROTL, AKT ACAKRL ZARUTL, HWZSOLITR ZTYGKT CTSS AL A YOKT UKGLL HSAFL CTKT 
GKOUOFASSB EIAKAEMTKL OF MIT LMKOH MG CIOEI LTTD MG OM CITF MTDHTKTR OF AFR 
IASSGCOFU MITB'KT LODHSB RKACOFU OF UOXTL GF" HKOFEOHAS LHOMMST ROLMGKM, 
KTARTKL EGDOEL AKT WLT, CAMMTKLGF MGGQ MCG 16-DGFMIL AYMTK KTLOLMAQTL A DGKT 
EKTAM RTAS MG EASXOF GYMTF IGZZTL MG ARDOML "LSODB, "ZWM OM'L FADTR A FOUIM GWM 
LIT OL HGOFM GY FGM LTTF IGZZTL MIT ZGGQL AM MIAM O KTDAOFOFU ZGGQ IADLMTK IWTB 
AKT AHHTAKAFET: RTETDZTK 6, 1995 DGD'L YKADTL GY EASXOF UOXTF A CAUGF, LGDTMODTL 
MIAM LG OM'L YAMITKT'L YADOSB FG EAFETSSAMOGFLIOH CAL HKTLTFML YKGD FGXTDZTK 21, 
1985 SALM AHHTAK AZLTFET OF AFGMITKCOLT OM IAHHB MG KWF OM YGK MIOL RAR AL "A 
SOMMST MG MGSTKAMT EASXOF'L YADOSB RKACF ASDGLM EGDDTFRTR WH ZTOFU HTGHST 
OFLMAFET, UTM DAKKOTR ZB A RAFET EASXOF'L GWMSAFROLOFU MIT FTCLHAHTK GK MAZSGOR 
FTCLHAHTK ZWLOFTLL LIGC OL GF!" AFR LHKOFML GY EIOSRKTF'L RAR'L YKWLMKAMTR ZB 
MWKF IWDGK, CAL HWZSOE ROASGU MITKT'L FGM DWEI AL "'94 DGRTKFOLD" CAMMTKLGF IAL 
RTSOUIML GY YAFMALB SOYT CAMMTKLGF LABL LTKXTL AL AF AKMOLML OL RTLMKWEMOGF 
ZWLOFTLL, LHAETYAKTK GY MIT GHHGKMWFOMOTL BGW ZGMI A MGHOE YGK IOL IGDT 
MGFUWT-OF-EITTQ HGHWSAK MIAM OM CAL "IGF" AFR JWAKMTK HAUT DGKT LHAEOGWL 
EAFETSSAMOGF MIT HAOK AKT ESTAKSB OF HLBEIOE MKAFLDGUKOYOTK'L "NAH" LGWFR TYYTEM 
BGW MIOFQTK CAMMTKLGF ASLG UKTC OFEKTROZST LHAET ZWBL OF EGDDGFSB CIOST GMITKCOLT 
OM'L FADT OL FGMAZST LMGKBSOFT UAXT MIT GHHGKMWFOMOTL BGW EAFETSSAMOGF MIT "EASXOF 
GYYTK MG DAQT IOD OFEGKKTEM AFLCTKL CAMMTK AKMCGKQ GMITK GYMTF CIOEI OL TXORTFM MG 
GMITK LMKOH OL MG MITOK WLT GY KWSTL MIAM LIGCF GF LAFROYTK, CIG WLTL A EKGCJWOSS 
ZT LTTF "USWTR" MG MIT GFSB HTKL AFR IOL YAMITK LWHHGKM OL SWFEISOFT UAXT MITLT 
MIOF A BTAK OF DWSMODAMTKOAS AFR GZMAOF GF LAFMALB, IOL WLT, CAMMTKL ROASGUWT OL 
AF "AKMOLM'L LMAMWL AL "A ROD XOTC OF MIT TLLTFMOASSB MG DAQT IOD LTTD MG OFESWRTR 
MIAM EASXOF OL AF GRR ROASGUWT DGLM GY MIT ESWZ IAL TVHKTLLOGF GWMLORT AXAOSAZST MG

You can either read from a file or hardcode the text in your script. The choice is yours.

Remember ANSI codes?

$ echo "\033[1;34m I'm blue... aba di... aba die... aba di aba die...\033[0m"

In breaking a short substitution cipher like this while also knowing the original language, you need to look at bigrams and trigrams. Small group of letters that have a limited amount of possible values that make sense: “to”, “and”, “the”, etc.

If you need an extra hint: <spolier> “RTETDZTK 6, 1995” looks like a date. Hmm… </spoiler>