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下面是一段经过经典密码算法加密的密文（加密算法未知）：
yvvnerujjvnywhbdvkpchfgvjtzwqsuporqfzpoekkjgziicdwwkeejdsruef
whwseyejejhnaeepjbjwnuztavjswrthswlcdxqrnoclsodkrrfjtfhlfznbx
wyvdwdcwyzqlqrnevuiiienxzmwtdsyhgstwmvznrvhyihhcxjijhiojphvjw
srpejwnhrhirqbcdwnzqmwjpoibnbjdeshloewcfdhvzjgtdwsvntydyweyll
gjrrohfuyplppzrssvniejxhzjtrwyvvdecpttrieevhzlxsvunstovzwjfsa
svlsgzjcvwmseioidhsywsddisrjadhkcideivjzwwsfqjcwphvwtdtkatkjg
zjwfpjbjbofwgochaegfhmyodpjbkwtfukcixokkrseoaegbcdanjitckxaco
xvvdajdqgfxetrrskdewlwgketronoesoddshfxezqiitpeulshfdeiftiepr
pvkcfpbroqwechroqcwbadhfbuwlcwmokshzojkfnkzqlojhanbjfzjhvuxdr
neklrskdezqiswwtzjfpcamfufqvolrwjgkreewzfvesrvftzbauhasckpdhs
hzjskuzqkkrydawecjlvyqfjdlfysuwcfxwgvhajwbsvgbvwbsvjaegtqkkbv
ufhkdezufbzwnwrthswlcdhouamplshvdrrqyvvnejkjhiwiehiwiwnzdskfi
eershyatvfmbzyacdxdvytjrkqfwcylsunkmvqxtfktsdqzektaxxhwkokefz
cxukvustefzffzcuwfpjbjbofwgochwyrjjvnsrbxhywtkkjavjsxdrsrjdkk
jkfieevlodaaihyvvoadhmojylvdwzpjemhwkfnkvgnbrlrfijgjeoedqseri
irsavjtjkjhfhdwlkotkmrvritdajztavjswrthswlckfgxnonqtjvntyhqoj
pfvzistwdvvnhywsewgstkmvdsmdkrvvnazhaiwthyamvqxurienrrsewrvsm
mjecroqmuefwhwseptfpjbrjdkkjafnekkjkfieevlodadvyjzflskkjafnez
wngwqlcrkggaczinqzpivvyvrprvtzwiaaulktvneewfdgnorfmtikmrftotd
jlvyzzgejddwerocojmswlcrwprokvwgochtyhwsjjogrnbkenxutigenxlyo
chuegjfkdejdrstwtvjtfpphvrgjzkujsmmjecroiwwbeihsqvoaihtbcutyh
xhrntzqldfenkwmswkrdhwgknibhwocoogrnbkotfnjmkwcklhocziwijfvjc
vvfbuprrlswecmvwmcuotrnjomarpvnaghevafaghekkjdzcgplshyamzgizv
zrzoqgjdetrshzjuvgdclnedraskdakiwcdwmvqxhiwielsujasjltbrjdprz
fvhojwbvvnervlsearroqmjlernnbxbeddqsghaphwguknkwjbupotdwsrxol
wyvzokzqicwyodsjhzpimhssjoiedboiiugptfryeyrusjphrwismalfsrsep
ielywrpimhxzzgekkjkfieevkcfpbroqqfwcylsutkuivjwepeyufbnditkbo
jwtkhsrvzbpztavjoeodkzhlyhqdkknruwcnphvjfdsatnhjbkdefsucipuel
ywvoawitfuadkrrocaaegksdwlvftotdejrkqfqrjhdcldamhlfvwttrfqyas
kkfhljdvuxhrjdkkjkfieevlodalznjoepoeltqrxrzqnweetrodcilhzondg
abvulsikozqkfrjcvvfwuioidhssqtnkfhjprznjgdaijzmseoodhysrisfuh
zlxstktcjahvdiqfwcyhxbfpbrvjrfjaivzafneosjfzanthgikkncbgstwuj
hyvvuhrsuseposhrsewszvfwuxewrwskdexdrszodziksiankdsrkdakvhzvw
rkrjjvnyfqjplptyhtdgkrkxswkeejdktfndvgyctkatkjgjdoloibkxeulkt
vneewtdgkrkxswkeejitfrhlkkjufopvoyvrpmfufqvesgujotdiejnggwrkl
hicwrcbaocqasojwephvpnruhevdxhndeihqokalpztavjswrthswlckfgdwd
vgwodwtzfxhiedvvnfrjffujlripchkwvhdjztavjsedywfjacwjodofirroc
hcrwjufnivvxhrntzqlokqaegnhjjakltbrhlvdlivberwzfvotvdrgzjtyhk
wiotulawjeoedsrrjokkjfwevvlshyasvftbuzimlxwfjnfwycdankltbrpok
dqtlpsroysrisjswsrzatutgjboluiwwbeihshcaaxxjrzrijltbjwtwlwgkc
lrqhszpsvdxmwkrnhxhvnnjwthvjdkryvzjkkkfhkdijlxotkmgojhvhyulkt
vneewhicpuihgikdoehxhcuajdswkwlzdskywtjwwitgmvwmsdkskzjfvphvv
nazhailywvosrliafnathusfllvdwsnwrddsrrlpirfqywbchfbuphvujgekp
cdhsndeihyvrpijdxqcaaidxwebofwgochwydywjavzgjbkpodhnbkahidswj
wgzjfbkecgdxgzknwrwtfktsdqzrhemhqcwenkhwsjptydygknucbtikotrqi
wecsghhwwecroqmrioejyvvsodhshykuxknhjylvdwhywtkknggwsjltbtwri
ljgrlokhshzwlnknqyesfqqmekwshnbxqnkdudvzhfsjtlhlpwmwjyoluxszo
aelrdfntrqygkapkrboizskkngdwhuljafdadpfrbdaelfavibvuttkdezufb
zwnwdxkfieevhcdiikwjswqlcbfuiaejznhyphvitfdarzwfzpwnuffbrzatr
fqysodhsgwkokefzcdajiqclnijkjrzjrvfjbkueruxoeznfzfrruszwxhyam
fvydflucdwggkrkdrceciidswrjwfpjbjdejdnrzpsroxcfjefiyvvbamrzfz
pejstfkoffurijhidztavjbvffijatyhdoiaacotkvztfsqopshzojkvwrzql
oyaauvhoibmfkfadwdbkfbzwljrgsceemhxhywttrrpzjakltbfbdvyjzflmv
qyqfqrjhxoezeclystkmghywkeoevqwbanvaymvwrjintrqwfpjbjsoioiwef
oigfbkdewlwgksodhsgnkrcghigdecgnbkdedlircaervyoiatyhbopboizff
uboiwmsiagzrswkoaxujokkpgrwhljikbycrptidhhgqbclhcgenzrshfsodh
sgwkokefzcwnudqgfboiijarhedlircaervysijtvdrgkksyrbhyaiivyfvjg
Kkxoxwievywepeiqfhzknrotdgknvqygjdetrsqcqdvg
破解过程：
1.先确定是单表还是多表加密，通过统计字母频率
把密文复制到Ciphertext处，点击左侧Freq，就有统计字母频率的功能。
统计结果：
a 120 0.034
b 91 0.026
c 105 0.030
d 178 0.051
e 178 0.051
f 164 0.047
g 99 0.028
h 180 0.051
i 148 0.042
j 205 0.058
k 201 0.057
l 111 0.032
m 55 0.016
n 113 0.032
o 146 0.041
p 85 0.024
q 82 0.023
r 193 0.055
s 168 0.048
t 139 0.039
u 87 0.025
v 177 0.050
w 210 0.060
x 63 0.018
y 97 0.028
z 126 0.036
可以选择用图表的形式显示出来：
可以看到字母频率分布的较平均，没有某个字符概率很高或者概率很低，所以猜测这是一个多表加密的密文。（因为单表加密通常都会显示出语言的特征）
现在已经知道是多表加密了，那用的是哪种多表加密算法呢？
实际的办法就只能一个个尝试。
首先假设这是一个Vigenere密码算法加密的密文：
先要确定密钥的长度
用CAP的Kasiski，得知
String Distance
yvv 273
yvv 707
yvv 868
yvv 1953
yvv 2765
yvv 3101
Yvv出现的距离：434 595 1680 2492 2828
最大公约数是7
猜测密钥的长度是7
再用CAP的Low Freq
输入密钥的长度7，给出的可能密钥是forward。
用CAP的Vigenere Cipher，输入keyword:forward，给出的原文是
there are very few people as entitledtoanalysethesimilaritiesanddif
ferencesbetweenmensandwomensfootballascarolinamoracefollowing
ayearplayingcareerduringwhichshebecamewidelyrecognisedasthegr
eatestitalianwomaninhistoryinshebeganacoachingcareerthatinclu
dedashortbutpioneeringstintatthehelmofamensclubseriecsviterbe
seinsincethenmoracehasmadeanameforherselfasoneofthetopcoaches
inwomensfootballandatvcommentatorforbothmensandwomensfootball
shehasalsobecomethefirstitalianwomantobeinductedintohercountr
ysfootballinghalloffameandallthatwhileworkingaslawyerinherspa
retimetheindefatigablemoraceslatestventureisasafifadevelopmen
tinstructorhavingjustconductedacourselastweekbetweenandoctobe
rattheiranianfootballacademyintehranthereshetrainediranianwom
enonthetechnicalaspectsofcoachingwomensfootballnotjustfootbal
lbutspecificallywomensfootballwhoeversaysthatthemensgameandth
ewomensgamearethesamehasclearlyneverworkedinaprofessionalenvi
ronmentshetoldfifacomasmuchaswomensfootballhasgrownoverthelas
tfewdecadesithasntbecomeanymoresimilartothemensgamewomenareph
ysicallydifferenttomenandthemorethewomensgamedevelopsthemorei
tisfullofspecificitiesthatrequireadifferentapproachfromacoach
justlikesayinvolleyballorbasketballtheresnopointingroupingita
llunderthesamecategorytheobviousphysicaldifferencesareonlythe
startingpointtheformerstrikeralsopointstokeytacticaldifferenc
esandtrainingmethodstakeaverysimpleexamplethepiggyinthemiddle
drillsshecontinuedyouremovethatfromamenstrainingsessionandyou
relostwhereasgenerallyspeakingfemaleplayersdonttendtocareabou
tthiskindofcompetitivenessinawarmupmoracehopesthatdevelopment
initiativeslikethewomensfootballcoachingcourseintehranwhichwa
sattendedbywomenonlywillhelptonarrowthegapbetweentheopportuni
tiesaffordedtomaleandfemalecoachesofcourseyouhavegreatcoaches
thatunderstandthewomensgamelikeantoniocabriniinitalyorphilipp
ebergerooinfrancesaidmoracebutwhatstrikesmeiswhensometeamsorc
lubschooseheadcoachesnotbasedonarsumorexperiencebutonlybecaus
etheyhappentobemenasisaidbeforethegameisdifferentandthatsclea
rtoeveryonebuttheopportunitiesaffordedtocoachesshouldntbediff
erentopportunitiesforallthegospelthatmoraceispreachingisparti
cularlyvaluableinthemiddleeastwherelatelywomensfootballhasmad
edramaticstridesiranforexamplefieldswomensnationalteamsfromal
lcategoriesstartingatuanditsnationalleaguefeaturesteamsinthef
irstdivisionandanotherfiveintheseconddivisionnottomentionatot
alfutsalteamsspreadacrossfourdifferentleaguedivisionsatfirstg
lanceitseasyforwesternstotendtothinkthatthisisacompletelydiff
erentculturebuthonestlyasanitalianwhatstruckmethemostwerethes
imilaritiessaidmoracepeoplearewarmandapproachableandtheresnop
lacewherethatisasclearasinfootballwhatisevidenttomeintehranis
agiganticpassionforfootballalevelofinterestthatstrulyoutstand
ingspecificallyamongthewomenthoughitsclearthatthispassioncarr
iesapotentialwhichisonlynowbeinguntappedhopefullythiscourseis
animportantsteptowardsthismahdiemohammadkhaniamemberoftheiran
ianfaswomenscommitteefullyagreeswiththeformeritalyandcanadaco
achwomensfootballhasflourishedinrecentyearsandnowadaysitsthem
ostpopularsportamongiranianwomenshesaiditsalsooneofthefavouri
tesportsformuslimwomenbecausetheyareallowedtoplaywhilewearing
aheadscarfmohammadkhanialsobelievesthatcombinationofdevelopme
ntcoursesandelitecompetitionslikenextyearsfifauwomensworldinj
ordanthefirstwomensworldcupheldinthemiddleeastarethewayforwar
dfortheregionitsagreatopportunitytoattractpublicopiniontowome
nsfootballandalsoforfemalemiddleeasternteamstoshowtheirstreng
thsagainstinternationalopponentssheconcluded
发现译文是有意义的，就把这个密文破解了。
如果发现译文是无意义的，就需要假设别的加密算法，根据假设的算法来使用相应的解密方法。
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原文地址：http://www.cnblogs.com/13jhzeng/p/5514541.html
