The following mystery fragment of ciphertext is known to be encrypted using a mon-alphabetic substitution cipher. FLISM QQZLI MCZNT SYTVZ LIHBP IMXIX ICMQQ IHNHT STZPS TFLTF ZTAQM RILNR ABZXM ZLIXN ZMUUI MXYZT AIMYN LMDIY MNHZL MZNTB ELZZT TVVIX LNRVT XNRNZ MZNTS ZTMQQ ZLTYI FLTAJ ZLIVT XZBSI TXZLI MXRYT VTZLI XYMXI XMNYI HZTET DIXSR ISZAI CMBYI LILMD NSEMQ TVZJY UNXNZ MSHVM XXIMC LNSEM NRYCT BQHST ZLMDI XIEBQ MZIHL NYCTS HBCZT ZLIXF NYIMS HTSQJ ZLIYL TXZSI YYTVZ LIQNV ITVMQ IGMSH IXMSH LNYTF SYNCP SIYYV First we run a count of the frequencies of the various characters, and a few of the top bigrams. The only reason for printing out the top 26 is typographic convenience. char count percent bigram count percent I 38 11.515 ZL 12 3.647 Z 32 9.697 LI 11 3.343 T 32 9.697 IX 9 2.736 M 30 9.091 IM 7 2.128 L 25 7.576 ZT 6 1.824 N 22 6.667 TV 6 1.824 X 21 6.364 XI 5 1.520 Y 20 6.061 TS 5 1.520 S 20 6.061 SH 5 1.520 Q 13 3.939 MX 5 1.520 V 12 3.636 MQ 5 1.520 H 12 3.636 LN 5 1.520 C 8 2.424 YT 4 1.216 B 8 2.424 YI 4 1.216 R 7 2.121 TZ 4 1.216 F 6 1.818 TX 4 1.216 E 5 1.515 NY 4 1.216 A 5 1.515 NR 4 1.216 D 4 1.212 MZ 4 1.216 U 3 0.909 MS 4 1.216 P 3 0.909 LT 4 1.216 J 3 0.909 LM 4 1.216 G 1 0.303 IY 4 1.216 W 0 0.000 IH 4 1.216 O 0 0.000 ZN 3 0.912 K 0 0.000 ZM 3 0.912 Total character count, 330. Total bigram count, 329. Total counts plus ETAOIN SHRDLU suggest I = e, Z = t, consistent with bigrams. (The other possiblities for t are less consistent with bigram frequencies) If this is correct, then the bigrams would also that suggest L = h. (We also get this if we look for a trigram that could be "the") Making these substitutions gives FheSM QQ the MCtNT SYTV the HBP eMXeX eCMQQ eHNHT STtPS TFhTF tTAQM RehNR ABtXM the XN tMUUe MXYtT AeMYN hMDeY MNHth MtNTB EhttT TVVeX hNRVT XNRNt MtNTS tTMQQ thTYe FhTAJ the VT XtBSe TX the MXRYTVT the XYMXe XMNYe HtTET DeXSR eStAe CMBYe hehMD NSEMQ TVtJY UNXNt MSHVM XXeMC hNSEM NRYCT BQHST thMDe XeEBQ MteHh NYCTS HBCtT the XFNYeMS HTSQJ the YhTXtSe YYTV the QNV eTVMQ eGMSH eXMSH hNYTF SYNCP SeYYV The number of times "the" shows up suggests we are correct in this guess. We might next look for "a". T looks good, but there are three common bigrams beginning with T, and both o and i get to start three bigrams before a does. Also, there are no repeated trigrams beginning with T that might be "and" while still being consistent with our picks for e, t, and h. Checking M, we find MSH, three times, MQQ twice, and MXE twice. So M looks like a good possibility. FheSa QQ the aCtNT SYTV the HBP eaXeX eCaQQ eHNHT STtPS TFhTF tTAQa RehNR ABtXa the XN taUUe aXYtT AeaYN haDeY aNHth atNTB EhttT TVVeX hNRVT XNRNt atNTS tTaQQ thTYe FhTAJ the VT XtBSe TX the aXRYTVT the XYaXe XaNYe HtTET DeXSR eStAe CaBYe hehaD NSEaQ TVtJY UNXNt aSHVa XXeaC hNSEa NRYCT BQHST thaDe XeEBQ ateHh NYCTS HBCtT the XFNYeaS HTSQJ the YhTXtSe YYTV the QNV eTVaQ eGaSH eXaSH hNYTF SYNCP SeYYV This doesn't look too bad. Q is probably l to make aQQ (which shows up three times) into "all". Also, X looks good for r given the IX and XI frequencies giving {er, re} since {et, te} is the only other common {e?, ?e} pair, and we already know t. FheSall the aCtNT SYTV the HBP earer eCall eHNHT STtPS TFhTF tTAla RehNR ABtra the rN taUUe arYtT AeaYN haDeY aNHth atNTB EhttT TVVer hNRVT rNRNt atNTS tTall thTYe FhTAJ the VT rtBSe Tr the arRYTVT the rYare raNYe HtTET DerSR eStAe CaBYe hehaD NSEal TVtJY UNrNt aSHVa rreaC hNSEa NRYCT BlHST thaDe reEBl ateHh NYCTS HBCtT the rFNYeaS HTSlJ the YhTrtSe YYTV the lNV eTVal eGaSH eraSH hNYTF SYNCP SeYYV Still looks OK T is likely a vowel, either o or i, and probably o, because we have two instances of "T the", and i is an unlikely final letter. FheS all the aCtNo SYoV the HBP earer eCall eHNHo SotPS oFhoF toAla RehNR ABtra the rN taUUe arYto AeaYN haDeY aNHth atNoB Ehtto oVVer hNRVo rNRNt atNoS to all thoYe FhoAJ the Vo rtBSe or the arRYoVo the rYare raNYe HtoEo DerSR eStAe CaBYe hehaD NSEal oVtJY UNrNt aSHVa rreaC hNSEa NRYCo BlHSo thaDe reEBl ateHh NYCoS HBCto the rFNYeaS HoSlJ the YhortSe YYoV the lNV eoVal eGaSH eraSH hNYoF SYNCP SeYYV The other vowel (i) must be N, Y, or S. S does not look good at all from bigrams - it shows up in only 2 of the 26 most common ones. If i is Y, then the most common bigrams beginning with i must be io and ie, which seems unlikely since in, is, and it are all more common. So let's try N = i. FheS all the aCtio SYoV the HBP earer eCall eHiHo SotPS oFhoF toAla RehiR ABtra the ri taUUe arYto AeaYi haDeY aiHth atioB Ehtto oVVer hiRVo riRit atioS to all thoYe FhoAJ the Vo rtBSe or the arRYoVo the rYare raiYe HtoEo DerSR eStAe CaBYe hehaD iSEal oVtJY Uirit aSHVa rreaC hiSEa iRYCo BlHSo thaDe reEBl ateHh iYCoS HBCto the rFiYeaS HoSlJ the YhortSe YYoV the liV eoVal eGaSH eraSH hiYoF SYiCP SeYYV Y and S are likely n and s. S = n would give us aSH twice as a possibility for "and" and ioS twice as a possibility for "ion", as well as being slightly more probably given the bigrams. Trying S = n and Y = s gives Fhen all the aCtio nsoV the HBP earer eCall eHiHo notPn oFhoF toAla RehiR ABtra the ri taUUe arsto Aeasi haDes aiHth atioB Ehtto oVVer hiRVo riRitation to all those FhoAJ the Vo rtBne or the arRsoVo the rsare raise HtoEo DernR entAe CaBse hehaD inEal oVtJs Uirit anHVa rreaC hinEa iRsCo BlHno thaDe reEBl ateHh isCon HBCto the rFisean HonlJ the shortness oV the liV eoVal eGanH eranH hisoF nsiCP ness V Suddenly some words are starting to show up. From the first word, it looks like F = w to give "when" and slightly further along, it looks like V = f to give "of". Let's also throw in our guess of H = d (to get our instances of "and") and try parsing some likely words out of what we get. when all the aCtions of the dBPe are reCalled i do not Pnow how to Ala RehiR ABtra the ritaUUe arsto Aeasi haDe said that i oBEht to offer hiR for iRitation to all those who AJ the fortBne or the arRsofo the rsare raised toEo DernR entAe CaBse hehaD inEal oftJs Uirit and farreaC hinEa iRsCo Bldno thaDe reEBl atedh isCon dBCto the rwiseandonlJ the shortness of the life of aleGander and his own siCPness f Starting to come together here. From the first line, looks like C = c, P = k, and B = u (to get "duke") From the second line, oBEht goes to ought if E = g. Making these changes and more parsing of likely words gives when all the actions of the duke are recalled i do not know how to AlaRehiR Autra the ritaUUe arsto Aeasi haDe said that i ought to offer hiR for iRitation to all those who AJ the fortune or the arRsofo the rsare raised to go DernRent Aecause he haDing aloft JsUir it and far reaching aiRs could not haDe regulated his conduct otherwise and onlJ the shortness of the life of aleGander and his own sickness f Mostly there now. From the last line, J = y, G = x, From the one above, R = m, D = v, and from the one above that, A = b. Substituting, and reparsing some errors in the word breaks when all the actions of the duke are recalled i do not know how to blame him but rather it aUUears to be as i have said that i ought to offer him for imitation to all those who by the fortune or the arms of others are raised to government because he having a lofty sUirit and far reaching aims could not have regulated his conduct otherwise and only the shortness of the life of alexander and his own sickness f With U = p, capitalization and puctuation. When all the actions of the duke are recalled, I do not know how to blame him, but rather it appears to be as I have said, that I ought to offer him for imitation to all those who by the fortune or the arms of others are raised to government. Because he, having a lofty spirit and far reaching aims, could not have regulated his conduct otherwise, and only the shortness of the life of Alexander and his own sickness f Which is a fragment from "The Prince" by Machiavelli.