Vigenère cipher/Cryptanalysis: Difference between revisions
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#37 = Search_Block("|V", Cur_Pos, EOL_Pos, ALL+NOERR)
Return </lang>
=={{header|Vlang}}==
{{trans|Go}}
<lang vlang>import strings
const encoded =
"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"
const freq = [
0.08167, 0.01492, 0.02782, 0.04253, 0.12702, 0.02228, 0.02015,
0.06094, 0.06966, 0.00153, 0.00772, 0.04025, 0.02406, 0.06749,
0.07507, 0.01929, 0.00095, 0.05987, 0.06327, 0.09056, 0.02758,
0.00978, 0.02360, 0.00150, 0.01974, 0.00074,
]
fn sum(a []f64) f64 {
mut s := 0.0
for f in a {
s += f
}
return s
}
fn best_match(a []f64) int {
s := sum(a)
mut best_fit, mut best_rotate := 1e100, 0
for rotate in 0..26 {
mut fit := 0.0
for i in 0..26 {
d := a[(i+rotate)%26]/s - freq[i]
fit += d * d / freq[i]
}
if fit < best_fit {
best_fit, best_rotate = fit, rotate
}
}
return best_rotate
}
fn freq_every_nth(msg []int, mut key []u8) f64 {
l := msg.len
interval := key.len
mut out := []f64{len: 26}
mut accu := []f64{len: 26}
for j in 0..interval {
for z in 0..26 {
out[z] = 0.0
}
for i := j; i < l; i += interval {
out[msg[i]]++
}
rot := best_match(out)
key[j] = u8(rot + 65)
for i := 0; i < 26; i++ {
accu[i] += out[(i+rot)%26]
}
}
s := sum(accu)
mut ret := 0.0
for i := 0; i < 26; i++ {
d := accu[i]/s - freq[i]
ret += d * d / freq[i]
}
return ret
}
fn decrypt(text string, key string) string {
mut sb := strings.new_builder(128)
mut ki := 0
for c in text {
if c < 'A'[0] || c > 'Z'[0] {
continue
}
ci := (c - key[ki] + 26) % 26
sb.write_rune(ci + 65)
ki = (ki + 1) % key.len
}
return sb.str()
}
fn main() {
enc := encoded.replace(" ", "")
mut txt := []int{len: enc.len}
for i in 0..txt.len {
txt[i] = int(enc[i] - 'A'[0])
}
mut best_fit, mut best_key := 1e100, ""
println(" Fit Length Key")
for j := 1; j <= 26; j++ {
mut key := []u8{len: j}
fit := freq_every_nth(txt, mut key)
s_key := key.bytestr()
print("${fit:.6} ${j:2} $s_key")
if fit < best_fit {
best_fit, best_key = fit, s_key
print(" <--- best so far")
}
println('')
}
println("\nBest key : $best_key")
println("\nDecrypted text:\n${decrypt(enc, best_key)}")
}</lang>
{{out}}
Note: carriage returns inserted into decrypted text after every 80 characters to make it more readable.
<pre>
Fit Length Key
2.984348 1 E <--- best so far
2.483684 2 EC <--- best so far
2.642487 3 TEE
1.976651 4 THEC <--- best so far
2.356881 5 EEEPU
2.203129 6 TCECEC
1.051163 7 THECSAS <--- best so far
1.645763 8 TJQGAHET
2.001380 9 VEIZSEGNT
1.824476 10 ECEGAWQTDS
1.623083 11 TNLUSRXPTAJ
1.253527 12 XLECTHQGTHEC
1.399037 13 LJJTDGFNOTENR
0.152370 14 THECHESHIRECAT <--- best so far
1.533951 15 JNTOOEEXFTGQTNH
1.068182 16 TJTSAEETEXHPXHNE
1.034093 17 AZRAXUHEJLREEXIEE
1.443345 18 VNIZQPALEPTSXSEXUC
1.090977 19 FUCAITCSLVTEZDUDEHS
0.979868 20 EQXGAHWTTQECEWUGXHPI
0.789410 21 HVRCSAFTHEBDLSTAERSES
0.881380 22 TVIJTCIGKAQPELECRXPTNC
0.952456 23 KKEQXGPWTCQEELIEHXUWASV
0.715968 24 ELAIXHQTTIEDXJETTNTGAEPC
0.891258 25 OTJUUEGERDNQTUQEAGWUTIEOA
0.852784 26 IGITEGECAGAVUNLJAHASAVTETW
Best key : THECHESHIRECAT
Decrypted text:
THISWASTHEPOEMTHATALICEREADJABBERWOCKYTWASBRILLIGANDTHESLITHYTOVESDIDGYREANDGIMB
LEINTHEWABEALLMIMSYWERETHEBOROGOVESANDTHEMOMERATHSOUTGRABEBEWARETHEJABBERWOCKMYS
ONTHEJAWSTHATBITETHECLAWSTHATCATCHBEWARETHEJUBJUBBIRDANDSHUNTHEFRUMIOUSBANDERSNA
TCHHETOOKHISVORPALSWORDINHANDLONGTIMETHEMANXOMEFOEHESOUGHTSORESTEDHEBYTHETUMTUMT
REEANDSTOODAWHILEINTHOUGHTANDASINUFFISHTHOUGHTHESTOODTHEJABBERWOCKWITHEYESOFFLAM
ECAMEWHIFFLINGTHROUGHTHETULGEYWOODANDBURBLEDASITCAMEONETWOONETWOANDTHROUGHANDTHR
OUGHTHEVORPALBLADEWENTSNICKERSNACKHELEFTITDEADANDWITHITSHEADHEWENTGALUMPHINGBACK
ANDHASTTHOUSLAINTHEJABBERWOCKCOMETOMYARMSMYBEAMISHBOYOFRABJOUSDAYCALLOOHCALLAYHE
CHORTLEDINHISJOYTWASBRILLIGANDTHESLITHYTOVESDIDGYREANDGIMBLEINTHEWABEALLMIMSYWER
ETHEBOROGOVESANDTHEMOMERATHSOUTGRABEITSEEMSVERYPRETTYSHESAIDWHENSHEHADFINISHEDIT
BUTITSRATHERHARDTOUNDERSTAND
</pre>
=={{header|Wren}}==
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