Vigenère cipher/Cryptanalysis: Difference between revisions
Added 11l
Alextretyak (talk | contribs) (Added 11l) |
|||
Line 29:
* Use that key to decrypt and output the original plaintext. Maintaining the whitespace from the ciphertext is optional.
* The algorithm doesn't have to be perfect (which may not be possible) but it should work when given enough ciphertext. The example above is fairly long, and should be plenty for any algorithm.
=={{header|11l}}==
{{trans|Python}}
<lang 11l>-V ascii_uppercase = Array(‘A’..‘Z’)
F vigenere_decrypt(target_freqs, input)
V nchars = :ascii_uppercase.len
V ordA = ‘A’.code
V sorted_targets = sorted(target_freqs)
F frequency(input)
V result = :ascii_uppercase.map(c -> (c, 0.0))
L(c) input
result[c - @ordA][1]++
R result
F correlation(input)
V result = 0.0
V freq = sorted(@frequency(input), key' a -> a[1])
L(f) freq
result += f[1] * @sorted_targets[L.index]
R result
V cleaned = input.uppercase().filter(c -> c.is_uppercase()).map(c -> c.code)
V best_len = 0
V best_corr = -100.0
L(i) 2 .< cleaned.len I/ 20
V pieces = [[Int]()] * i
L(c) cleaned
pieces[L.index % i].append(c)
V corr = -0.5 * i + sum(pieces.map(p -> @correlation(p)))
I corr > best_corr
best_len = i
best_corr = corr
I best_len == 0
R (‘Text is too short to analyze’, ‘’)
V pieces = [[Int]()] * best_len
L(c) cleaned
pieces[L.index % best_len].append(c)
V freqs = pieces.map(p -> @frequency(p))
V key = ‘’
L(fr_) freqs
V fr = sorted(fr_, key' a -> a[1], reverse' 1B)
V m = 0
V max_corr = 0.0
L(j) 0 .< nchars
V corr = 0.0
V c = ordA + j
L(frc) fr
V d = (frc[0].code - c + nchars) % nchars
corr += frc[1] * target_freqs[d]
I corr > max_corr
m = j
max_corr = corr
key ‘’= Char(code' m + ordA)
V r = (enumerate(cleaned).map((i, c) -> Char(code' (c - @key[i % @best_len].code + @nchars) % @nchars + @ordA)))
R (key, r.join(‘’))
V 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’
V english_frequences = [
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]
V (key, decoded) = vigenere_decrypt(english_frequences, encoded)
print(‘Key: ’key)
print("\nText: "decoded)</lang>
{{out}}
<pre>
Key: THECHESHIRECAT
Text: THISWASTHEPOEMTHATALICEREADJABBERWOCKYTWASBRILLIGANDTHESLITHYTOVESDIDGYREANDGIMBLEINTHEWABEALLMIMSYWERETHEBOROGOVE...
</pre>
=={{header|Ada}}==
| |||