September 2017 Update

Task/Vigen-re-cipher-Cryptanalysis/Phix/vigen-re-cipher-cryptanalysis.phix

@@ -0,0 +1,208 @@
+--
+-- demo\rosetta\Cryptanalysis.exw
+--
+atom t0 = time()
+constant ciphertext = substitute_all("""
+MOMUD EKAPV TQEFM OEVHP AJMII CDCTI FGYAG JSPXY ALUYM NSMYH
+VUXJE LEPXJ FXGCM JHKDZ RYICU HYPUS PGIGM OIYHF WHTCQ KMLRD
+ITLXZ LJFVQ GHOLW CUHLO MDSOE KTALU VYLNZ RFGBX PHVGA LWQIS
+FGRPH JOOFW GUBYI LAPLA LCAFA AMKLG CETDW VOELJ IKGJB XPHVG
+ALWQC SNWBU BYHCU HKOCE XJEYK BQKVY KIIEH GRLGH XEOLW AWFOJ
+ILOVV RHPKD WIHKN ATUHN VRYAQ DIVHX FHRZV QWMWV LGSHN NLVZS
+JLAKI FHXUF XJLXM TBLQV RXXHR FZXGV LRAJI EXPRV OSMNP KEPDT
+LPRWM JAZPK LQUZA ALGZX GVLKL GJTUI ITDSU REZXJ ERXZS HMPST
+MTEOE PAPJH SMFNB YVQUZ AALGA YDNMP AQOWT UHDBV TSMUE UIMVH
+QGVRW AEFSP EMPVE PKXZY WLKJA GWALT VYYOB YIXOK IHPDS EVLEV
+RVSGB JOGYW FHKBL GLXYA MVKIS KIEHY IMAPX UOISK PVAGN MZHPW
+TTZPV XFCCD TUHJH WLAPF YULTB UXJLN SIJVV YOVDJ SOLXG TGRVO
+SFRII CTMKO JFCQF KTINQ BWVHG TENLH HOGCS PSFPV GJOKM SIFPR
+ZPAAS ATPTZ FTPPD PORRF TAXZP KALQA WMIUD BWNCT LEFKO ZQDLX
+BUXJL ASIMR PNMBF ZCYLV WAPVF QRHZV ZGZEF KBYIO OFXYE VOWGB
+BXVCB XBAWG LQKCM ICRRX MACUO IKHQU AJEGL OIJHH XPVZW JEWBA
+FWAML ZZRXJ EKAHV FASMU LVVUT TGK""",{" ","\n"},{"",""})
+
+constant letters = new_dict(
+   {{'E',12.702},
+    {'T',9.056},
+    {'A',8.167},
+    {'O',7.507},
+    {'I',6.966},
+    {'N',6.749},
+    {'S',6.327},
+    {'H',6.094},
+    {'R',5.987},
+    {'D',4.253},
+    {'L',4.025},
+    {'C',2.782},
+    {'U',2.758},
+    {'M',2.406},
+    {'W',2.361},
+    {'F',2.228},
+    {'G',2.015},
+    {'Y',1.974},
+    {'P',1.929},
+    {'B',1.492},
+    {'V',0.978},
+    {'K',0.772},
+    {'J',0.153},
+    {'X',0.150},
+    {'Q',0.095},
+    {'Z',0.074}})
+constant digraphs = new_dict(
+   {{"TH",15.2},
+    {"HE",12.8},
+    {"IN",9.4},
+    {"ER",9.4},
+    {"AN",8.2},
+    {"RE",6.8},
+    {"ND",6.3},
+    {"AT",5.9},
+    {"ON",5.7},
+    {"NT",5.6},
+    {"HA",5.6},
+    {"ES",5.6},
+    {"ST",5.5},
+    {"EN",5.5},
+    {"ED",5.3},
+    {"TO",5.2},
+    {"IT",5.0},
+    {"OU",5.0},
+    {"EA",4.7},
+    {"HI",4.6},
+    {"IS",4.6},
+    {"OR",4.3},
+    {"TI",3.4},
+    {"AS",3.3},
+    {"TE",2.7},
+    {"ET",1.9},
+    {"NG",1.8},
+    {"OF",1.6},
+    {"AL",0.9},
+    {"DE",0.9},
+    {"SE",0.8},
+    {"LE",0.8},
+    {"SA",0.6},
+    {"SI",0.5},
+    {"AR",0.4},
+    {"VE",0.4},
+    {"RA",0.4},
+    {"LD",0.2},
+    {"UR",0.2}})
+constant trigraphs = new_dict(
+   {{"THE",18.1},
+    {"AND",7.3},
+    {"ING",7.2},
+    {"ION",4.2},
+    {"ENT",4.2},
+    {"HER",3.6},
+    {"FOR",3.4},
+    {"THA",3.3},
+    {"NTH",3.3},
+    {"INT",3.2},
+    {"TIO",3.1},
+    {"ERE",3.1},
+    {"TER",3.0},
+    {"EST",2.8},
+    {"ERS",2.8},
+    {"HAT",2.6},
+    {"ATI",2.6},
+    {"ATE",2.5},
+    {"ALL",2.5},
+    {"VER",2.4},
+    {"HIS",2.4},
+    {"HES",2.4},
+    {"ETH",2.4},
+    {"OFT",2.2},
+    {"STH",2.1},
+    {"RES",2.1},
+    {"OTH",2.1},
+    {"ITH",2.1},
+    {"FTH",2.1},
+    {"ONT",2.0}})
+
+function decrypt(string enc, string key)
+integer keylen = length(key), k = 1
+    string msg = repeat(' ', length(enc))
+    for i=1 to length(enc) do
+        msg[i] = mod(enc[i]-key[k]+26,26)+'A'
+        k = mod(k,keylen)+1
+    end for
+    return msg
+end function
+
+function cryptanalyze(string enc, integer maxkeylen=20)
+    integer enclen = length(enc)
+    string maxkey = "",
+           maxdec = "",
+           k1 = " "
+    atom maxscore = 0.0
+
+    for keylen=1 to maxkeylen do
+        string key = repeat(' ',keylen)
+        sequence idx = {}
+        for i=1 to enclen do
+            if mod(i,keylen)=0 then
+                idx &= i-keylen+1
+            end if
+        end for
+
+        for i=1 to keylen do
+            atom maxsubscore = 0.0
+
+            for j='A' to 'Z' do
+                atom subscore = 0.0
+
+                k1[1] = j
+                string encidx = ""
+                for ii=1 to length(idx) do
+                    encidx &= enc[idx[ii]]
+                end for
+                string dec = decrypt(encidx,k1)
+                for di=1 to length(dec) do
+                    subscore += getd(dec[di],letters)
+                end for
+
+                if subscore > maxsubscore then
+                    maxsubscore = subscore
+                    key[i] = j
+                end if
+            end for
+
+            idx = sq_add(idx,1)
+        end for
+
+        string dec = decrypt(enc, key)
+        atom score = 0.0
+
+        for i=1 to length(dec) do
+            score += getd(dec[i],letters)
+        end for
+
+        for i=1 to enclen - 2 do
+            string digraph = dec[i..i+1]
+            string trigraph = dec[i..i + 2]
+            score += 2 * getd(digraph,digraphs)
+            score += 3 * getd(trigraph,trigraphs)
+        end for
+
+        if score > maxscore then
+            maxscore = score
+            maxkey = key
+            maxdec = dec
+        end if
+    end for
+
+    return {maxkey,maxdec}
+end function
+
+function fold(string s, integer w)
+    for i=w to length(s) by w do
+        s[i..i-1] = "\n"
+    end for
+    return s
+end function
+
+string {key, dec} = cryptanalyze(ciphertext)
+printf(1,"key: %s\n\n%s\n\n", {key, fold(dec,80)})
+
+printf(1,"elapsed time: %3.2f seconds",{time()-t0})