(phixonline)-->
--
-- demo\rosetta\Cryptanalysis.exw
--
with javascript_semantics
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})
{} = wait_key()