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The National Cipher Challenge

Challenge 6

RULE REMINDER: Rapid fire multiple submissions put an unreasonable load on the servers and make it difficult for others to submit. Anyone who makes an unreasonable number of submissions will be open to disqualification. In the first instance this will mean that anyone who submits more than 20 times in 10 minutes will be disqualified.

Unless you are a very experienced codebreaker it is really important that you read the hint for this one, so do click on the TIPS button to help you get started. (Unless you like a difficult challenge! I suspect Madness will manage this with a blindfold on.) You will have to do quite a lot of work, but I have laid out what you need to do to break it and the practice will be useful.

Cryptic clues

YLRPC CHGHS CHLYC UNJUG UJSZB CTJZB PWKGB EENGB CURGZ TJSLZ UECLR XIZSU IGBEP GKBDJ BGBDP JLCTU MCYLZ LSCRU BJZSL JGLJC JRLTL AUMLJ UNTLT JYTAC UILZC BIJYE BLBJG KLSLX GTDCI CJIJZ BUIRZ CTLMC HZLLG ZZKUU SZJIZ BCXDY LOLJJ JZULL AGDRL JEYBG JJLTG EECUC DAIZU ISGTJ BTSKJ IBTLE EBUIL AULSZ ZCGLX LPYZZ USLIG LTLMC HZLLT TSUXY UPDIL GIHRL PKBPG ALYTU ZCITJ YLLNP GICLJ UZBIR LTCTJ JLLDI LUNRJ TNTUU TAJIC NCLXH JCDBG JLITG JLCUE EARZC JBABG ALGJE PXXYS CLCII SJILT RJCLG LIMGB LGKFL USLGG JCLLJ CGJJZ LUAZB KBUGK PXITL NBMBG LZEBL JJLTL SLXGI YCTGI CLIUI JCRLJ ACJWJ BHTPP HBAGK BKDYJ CGLZP HRYGA PPBJD XUSBI RIJLU DIJTJ LLCGU ZPYRH JILLB EEGJI JTNPL LKLGZ XHCLR BJLGL JYLZU JZLTC GKJLJ EBTLJ LOJUJ AJZBC IZUJJ LTLZT AUCUA ZBTNH KBGSK JTIKB PGCXD ZCJIW JILTU MLLTJ NCTJJ LILYI LSCYT PCCHL MLLZL ZPGAD RLJKZ UISUM CSLZL GUALD GLTCJ RZTLI LCBLG EKBAG ZLIBG BJUIK BXURP EAUEK JJXBL GHCLD WGDCT INJUU GXXLI UIJCI KXZUX NAUTT ICALY CUCCG EUTJR CUYJS KJTZG LRYLZ UJMLT CLKXB TJEUZ LIRMC LBUGK CBTYD SZUJJ CTPBK BGKBP GUGEL NRZTJ CLIZB JLSUY TLHJC LXHIS SKLCJ IYURB ECAUJ ZBUBB PEKCY GAZUT LCTJJ ZCAGL IUJTJ BLCTA XZLXS AULCG DZBRU MLLZB KELIK JUXLE BYULJ ZXSUX LLAZJ JCTYT PCLUD XZALR ULTDG SZUJA LTKLI GRXLJ LCGSY NJUCD CIDLG CZPXJ IJZLE YBGJB LTEAU ELCEB ZPNLB HWGKZ UILYI ICPHZ JZLTC BLYEX UYXCG LZCYR PMCTL LLHZL GCDJP XBBZC JGLTY IILCE LSGIY BBBLY ZUILS ZUZSJ UNTLT JISZU XLXLJ GLJGK YUIBA JZCGS JCXKJ BPLKL JGAUZ TAZCU EYGBC ZUWSU TJIZB AZJAL UJZBT ZULJA GLLLJ DRILY ILSCJ UYBXG LXEYB GGICN LGAZP LJDRU IKZIC SUXDY LLCAI IGCTJ EUATD ULTNG UTTAC BZRZT JLLIL XIKCA ICRLI NBXRZ NBUTJ ZLDDC CJCGK NBIUJ SZBLT JEJAC JJCTJ JLTLT JOCLH RLXHZ BLWAR EZUUX LMLLJ JGBGS KNIDT LXUNJ UCUES ZBTJG LSZLU LLZGB JIJLZ KJYLT LCTAZ YIUJD IBLKR LDLTJ RGALP UJDBB PZKBA GXCLX SALKG WACLT JRCUA JDGLT HCTPZ ZCRRG LAJZU CCLDI ABIJE UJUZK XARSZ UJKLT IEBLC JUZCC UXZGB EYYEB ULXXG CZIYJ CLJAC GJTRL LJCGJ JZLUI ZBLUJ JZECS XJSCB ZBYUG BJYII LCILS EYBGJ ZLTLT SUHGK BTRBB BUEEA LXLRJ BJTUR LIMBA LBPGE UTJIO LJJTJ UUUWZ JDIUL CTGDB NIGLT JOUYC ZSZUE JGKTU GLEXZ BPTBJ LUDXY BGDMB PLKLY GAZCT URYIB LSR

The Device

Official Decrypt

Top Secret: For your eyes only

My dear Babbage, I am writing to thank you for forwarding the final designs for your prototype. I have managed to integrate the device with the machines at some of our telegraphs stations and have been running it on sample text intercepted from the traffic passing through those offices. In general, my engineers have been highly impressed by your mechanism. They were astonished at the speed with which it was able to parse the traffic and to correctly flag messages that deserve or require greater attention. Curiously, however, one of the telegrams has resisted attack both by your computer and by my cryptologists. Despite their (and my) best efforts they were unable to determine the nature of the text it contains. The technician who brought us your plans takes the view that the message may have been encrypted using a Vigenere cipher, and these are, of course, notoriously difficult to break. Perhaps it will resist us all, in which case I am afraid that might undermine the value of this endeavour. I am hoping that you or your friend Wheatstone might be able suggest a modification of your machine that can rise to the challenge. I can provide one useful item of intelligence that may help in deciphering the cursed telegram: it was apparently sent from the office of a New York businessman by the name of Miller, and may have been a reply to another message from someone signing with the single letter R. I must congratulate your technician for making this connection. The intercepted message to Miller from R was encrypted using a simple Caesar shift cipher, which had nonetheless caused a slowdown in the apparatus owing to the fact that the text had been blocked in five letter groups. While waiting for the engineers to tune the mechanism to speed up the decryption your colleague cracked that cipher by hand, and certain aspects of it, including the use of an Italian form of Miller’s name, attracted her attention. Setting a flag to monitor messages from the neighbourhood office led to the discovery of this text. I think it is perhaps worth examining further, if only to help improve your mechanism. Dodge

The wheels are turning

ZCZCO IBLSQ YFVMY IWPZP YSXDC JZOJX DYHZK AHIWQ FVYIW EIVCN VASBU OEZWJ IZXTA DYHZD VWPFO KIBYW PSFPS INGBX KAHEY ANBVX ELUKY NWOSF VIBYP FOKDU EPGGW KEJNM AKRRG WQSVF RREDW KGRVA WCLGV PHIBF GGLWR CKRRV HCGJC PVQNI CYHWX SGZXR WOKSE KEISG ZCSAK PMSOZ YSERW EQNRU YBUKY PELJV XGMKL GNSGL JMDRI ZIJRT FBGLA MFZQV RWRCI KAHSC FVWNM JWCLB FYNCG KQHEN YBKOR SBBIV BRGKK DVXFI NCBVQ BXEYH ZXTSQ PRVKY AEJZF XYCOJ CNYHV LPCXB RWOYB USSSP FSICT IPUWE NBJPF WJYCT KPHLX VXUWC LBVWG JCJSA KATSI IGLEL UPYHL WTSEO TSPGO KOQAE RVLCV XEQCW DUIDG UYOFX EKDFB GEJAS KRNXS CQFXP PQBSK RVWOR OXOBJ KSFTY YPWZC IKGMK LOJAH MYIZP KFTKQ GZLYI UMIYK IIPMZ UEFXD YHUSF THYBE SAKPM AVOGA ERVKR RTNCG ZNRRP QCFXN RZMBT OUIDY GRCFY NYBTO GLWRH YOTSR CFEWR RPQIG ZBVPQ VZCCP WLHYS AKOUW CVZSR CJVBL UQGQB VLMYY BEYGT NMAZC RXKFC CNZCE LJVCG SNQHF QRXDC FZPGL AWHYS AOPFS ZBVRP CFVCG WWPSS OGXAP GVBII ZCZJO JLAPS JYJMJ LWEQG LAGFW SEQYM ADSGQ ALHEY JMOGB RVYSQ PWEDR VAQHJ SGMOA FLMVE HRVRD LSQYB USPSJ TWEMR XDCAF PGLAT OCERS BRVZC CVKNS IDLEJ BMFEN VAZSJ DCPWA SUDBE YOIZB RXDCS MSQIJ ASWYE YOGII QRCKS HFLRK XMFIY JSNQH VKYEY MBTVH WETSU OZSJQ HIKGM KLCWD UIRYZ LOBJP FSGBB HQAHF BGSLP CMSQI WDICV RVZCG TBVTP GCEYS XDCDC YGMJM FUOEX DYHZM NRBGB RVYCL CFJEN HAKMW BVIJB GKYPS IKWKD BFWAY ZXTYO WCLBF EJVWF EFPUK CCSAE NM

You can try frequency analysis, and ultimately I think you will find it helpful, but at first it might not assist you much. You will know why if you have already broken part A, if not I suggest you do that first!

Official Decrypt

Top Secret: For your eyes only

My dear R, You are clearly of the view that I and my colleagues are undervaluing what it is that you are offering, and I am writing to assure you that that is far from the case. Even if it were, you will know that other less scrupulous businessmen are willing to exploiting any and all inventions with no payment for the originator and we remain your surest guarantee of due recompense. Renegotiating our deal will only slow our progress and if others get wind of this opportunity, you risk losing everything you have negotiated with us. It is of the highest importance that we conclude this stage of our collaboration as quickly as possible. You have told us that D is planning to meet with the President soon, and once he has assurance that the government supports his plan things will move very quickly. I cannot promise to hold my investors together if they think their interests are better served elsewhere, so winning their firm commitment now is in all our interests. It is crucial that you and I convince them of the value of this property, and you are best placed to acquire the evidence for us. I urge you to beg, borrow or steal a conclusive demonstration of the value of the product, or to provide a fuller description of the plot, in order that I can finally persuade my friends to commit to backing us. Yours anxiously, Molinaro

This challenge closed on 26/11/2025. Please click the Official Decrypt button above to see the correct answers.

RULE REMINDER: Rapid fire multiple submissions put an unreasonable load on the servers and make it difficult for others to submit. Anyone who makes an unreasonable number of submissions will be open to disqualification. In the first instance this will mean that anyone who submits more than 20 times in 10 minutes will be disqualified.

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