rot

破解下面的密文：

83 89 78 84 45 86 96 45 115 121 110 116 136 132 132 132 108 128 117 118 134 110 123 111 110 127 108 112 124 122 108 118 128 108 131 114 127 134 108 116 124 124 113 108 76 76 76 76 138 23 90 81 66 71 64 69 114 65 112 64 66 63 69 61 70 114 62 66 61 62 69 67 70 63 61 110 110 112 64 68 62 70 61 112 111 112

flag格式flag{}

看到題目，先看前面幾個字，83在ascii當中是s，rot13後是f，以rot13對每個字元進行解碼。

s = '83 89 78 84 45 86 96 45 115 121 110 116 136 132 132 132 108 128 117 118 134 110 123 111 110 127 108 112 124 122 108 118 128 108 131 114 127 134 108 116 124 124 113 108 76 76 76 76 138 23 90 81 66 71 64 69 114 65 112 64 66 63 69 61 70 114 62 66 61 62 69 67 70 63 61 110 110 112 64 68 62 70 61 112 111 112'
l = s.split(" ")
for i in l:
    print(chr(int(i)-13),end='')

初步解碼之後得到以下訊息

FLAG IS flag{www_shiyanbar_com_is_very_good_????}
MD5:38e4c352809e150186920aac37190cbc
import hashlib

demo = 'flag{www_shiyanbar_com_is_very_good_'
md5 = '38e4c352809e150186920aac37190cbc'

for i in range(32, 126):
    for j in range(32, 126):
        for k in range(32, 126):
            for m in range(32, 126):
                tmp = demo + chr(i) + chr(j) + chr(k) + chr(m) + '}'
                hash = hashlib.md5(tmp.encode('utf8')).hexdigest()
                if md5 == hash:
                    print(tmp)
                    exit()

進行md5爆破之後，可以解出來flag。

flag{www_shiyanbar_com_is_very_good_@8Mu}

[NPUCTF2020]这是什么觅🐎

下載檔案後打開來看是亂碼，開頭是PK，反射性將副檔名改成zip之後解壓縮。

解壓縮之後得到下圖。

圖片底部有標註數字。

F1 W1 S22 S21 T12 S11 W1 S13

T和S開頭的都有兩個，所以按先後順序有T1=TUE，T2=THU，S1=SAT，S2=SUN。

對日歷進行查表之後發現得到數字。

密文 解密後數字 對應字母
F1 3 c
W1 1 a
S22 12 l
S21 5 e
T12 14 n
S11 4 d
W1 1 a
S13 18 r

解出flag為calendar

浪里淘沙

提示: 我有密集恐懼症，所以大家自求多福吧，把獲得的單詞連在一起提交即可。（我這裡有一串數字：4，8，11，15，16）

題目:

tonightsuccessnoticenoticewewesuccesstonightweexamplecryptoshouldwebackspacetonightbackspaceexamplelearnwesublimlearnbackspacetheshouldwelearnfoundsublimsystemexamplesublimfoundlearnshouldmorningsublimsystemuserlearnthecryptomorningexamplenoticetonightlearntonightlearntonightsublimenterusermorningfoundtonightweenterfoundnoticethecryptomorningthebackspacelearntonightlearnsublimtonightlearnfoundenterfoundsuccesstonightsuccessuserfoundmorningtonighttheshouldsublimentertonightenterbackspacelearnexamplenoticeexamplefoundsystemsuccesssublimsuccessshouldtonightcryptowelearncryptofoundshouldsublimsublimweentertonightsuccessshouldentertheentercryptouserbackspaceshouldentersystemsuccesssystementerfoundenterlearnexampletonightnoticemorningusertonightlearnmorningtonightfoundfoundsuccessnoticesystementerlearnexamplebackspaceshouldcryptocryptosublimweexampletonighttheshouldthemorningbackspacelearntonightsystemsuccesssuccessbackspacemorningnoticeuserfoundfoundtonightmorningenterenterthefoundbackspacelearnenterentershouldthesystemfounduserlearnlearnsystemnoticetonighttheshouldlearnuserbackspaceweusernoticeshouldthewefoundsystemwecryptocryptowethebackspacesystementershouldtonightsystemnoticemorningsystemweentermorningfoundsuccessusertonightsuccesstonightbackspaceshouldweenterthewesystemusernoticesystemthelearnexamplelearnfoundlearnnoticeexamplesystemthecryptocryptolearnsystemthecryptoenterlearnexamplemorningmorningweenterentersuccessexampleuserthebackspacenoticesublimenterbackspacesuccessbackspacethesublimexamplesystemtheexamplecryptolearnuserexamplelearnsystemusersuccessenterentersuccesstheuserbackspacelearnsuccessbackspacethesublimshouldwebackspaceexamplesuccesssuccesstonightweusershouldsuccessmorningcryptomorningfoundbackspacesublimshouldentershouldnoticesuccessmorningsuccessexamplelearnshouldsublimlearntonightshoulduserbackspacesublimlearncryptosuccessenternoticetonightmorningtonightwesuccessweuserbackspaceexamplewesystemnoticemorningsystemmorningcryptolearnsystemthethefoundcryptouserlearnusersystemwemorningenterexampleshouldlearncryptofoundenterbackspacelearnenterenterbackspaceshouldbackspacetheshouldthesystemshouldshouldsuccessmorningthefoundsystementersystemtonightcryptowelearnexampleexamplesystementerbackspaceshouldtheentersublimtonightfoundfoundsuccesssuccesssystemsublimcryptoshouldentersublimmorninglearnfoundtonightcryptobackspacesuccesscryptowebackspacefoundshouldnoticeshouldmorningnoticesystemcryptosystemlearnsystemnoticemorningsystementerwemorninglearnsuccessfoundwesuccesswetheusercryptousernoticebackspacesuccessshouldtonightmorningentermorninguserenternoticefoundmorningwetonightsystemthecryptotonightcryptosystemuserthefoundexampletonightusersystemcryptosublimmorninguserthefoundbackspaceshouldsuccesscryptotonightsystemnoticebackspaceusershouldenterthecryptomorningwesublimnoticesuccessnoticeusersuccesstonightlearnweuserenterfounduserexampleshouldshouldtonightwelearnthenoticethewefoundmorningexampleshouldexamplethesuccessnoticeenterfoundthecryptonoticeuserlearnuserweenterfoundmorningsystemweexamplenoticethebackspaceexamplesublimtheusermorningtonightthesuccesscryptosuccessusersuccesstonighttonightwelearnenterenterthemorningentersystemcryptobackspacemorningsystemexamplecryptouserexamplelearnsublimsuccessusersystemfoundmorningshouldcryptotonightsublimtheexamplemorningsystemuserexampleweexamplenoticesuccesssublimnoticecryptoshouldbackspaceshouldthetonightfoundsublimbackspacebackspacetonightshouldbackspacesuccesstonightbackspacesuccessmorningsystemcryptobackspaceentertonighttonightnoticelearnshoulduserfoundexamplesystemthesuccessweusertonightcryptousernoticeenternoticebackspaceusersystemfoundusernoticeshouldlearnuserfoundexampleusermorningshouldsuccessmorningmorningexampleexamplefoundsublimfoundenterbackspacenoticelearnfoundmorningcryptonoticecryptoshouldweshouldtonightcryptobackspacesublimcryptosublimenterentersublimentercryptonoticethethesublimexampleenterentershouldlearncryptoentershouldmorninglearnnoticeuserexamplesublimtonightshouldfoundtonightsuccessshouldmorningfoundtheweuserlearnsublimsystembackspacecryptotheusertonightcryptosublimmorningmorningexamplenoticetheenterlearnshouldmorningsublimfoundtonightsublimsublimexamplefounduserexamplethefoundwemorningnoticefoundcryptosuccesssublimsublimexamplethesuccessexamplenoticesuccessbackspacesublimlearnuserexamplesuccesssuccesssystemsuccessmorningmorninglearnexamplemorningtonightfoundbackspaceenternoticemorningentersuccessmorningusermorningbackspacelearncryptoenteruserenteruserthetonighttonightsuccesslearnenterfoundsuccesssystemfoundbackspaceenterlearnsystemsublimcryptoentermorningwetonightshouldlearnenterfoundcryptonoticelearnlearnshouldfoundsuccessexampletonightthesuccessfoundusertonightenterfoundsuccessshouldmorningusernoticemorningsystemsystemsuccessshouldwelearnenterfoundexamplewethefoundweshouldsystemsystemmorningmorningbackspaceshouldentersublimentertonightsuccesssystemsystemcryptousershouldsublimfoundwetonightnoticeexamplewewesuccessfoundusertonightfoundsystemexamplecryptofoundshouldshouldsuccessenterbackspaceexampletonightthelearnnoticeuserlearnsystemsublimfoundlearnsuccesssystemshouldsublimnoticelearnsystemnoticetonightexamplefoundusernoticeenterlearnnoticecryptousersystemmorningthewesystemfoundfoundshouldsystementerenterbackspacesystemsublimcryptousermorninglearnlearntonightsublimlearnenterenterbackspacesystemuserusercryptoentershouldtheusersublimnoticeexamplemorningexamplesublimsublimbackspacesystemexampleshouldsublimlearnfoundenterbackspacelearnmorningmorningfoundthetonightmorningnoticeenterlearnusersystemtonightbackspaceexamplelearntonightbackspaceweshouldcryptosuccessbackspaceexamplesuccesstheshouldmorninguserbackspacelearnthetheshouldcryptocryptotonightbackspacecryptocryptobackspacebackspacenoticeusertonightentermorningfoundweenterexampleenterfoundusersublimsystemtheexampleexamplesystemsuccessusersublimentermorningbackspacesystemfoundlearnsystemshouldsublimsublimentershouldtheusershouldexampleexampleshouldsuccesswelearnfoundsublimshoulduserweentertonightwenoticesublimsystemlearnshouldfoundsuccessuserentersuccessmorningcryptoenteruserfoundexampletonightlearnexampleexamplefoundlearnsuccesssystembackspacecryptonoticethefoundbackspacelearncryptothelearnlearnexamplesuccessnoticenoticesystemmorningcryptotonightnoticenoticeentersuccesscryptoenterbackspacesublimexampleenterfoundtonightcryptotonightsublimnoticesuccesssublimtheentertonighttheshouldthefoundsystemtonightuserbackspacesuccessshouldwebackspacenoticebackspacebackspacenoticewecryptobackspacebackspaceusertonightlearnsuccessmorningusertonightsuccessshouldbackspacecryptoenterentershouldsublimsystemexamplemorningcryptonoticethesuccessthebackspacenoticelearnsublimlearnsuccesscryptothesuccessenternoticecryptosystemsublimsuccesswebackspaceuserenterlearnuserwewemorningsuccesslearncryptobackspacewecryptosystemlearnenterenteruserexamplefoundsystemcryptousernoticefoundusersublimbackspacewesublimnoticemorningshouldexamplenoticecryptoshouldtonightmorningthefoundsystementerentersystemthecryptobackspacesublimlearnsuccessmorningsublimsystemcryptousersublimwesuccessmorningsublimbackspacecryptobackspacesublimthelearnsuccesssublimlearncryptoweweexamplecryptowenoticelearnfoundbackspacesystemsystemexampleshouldlearnsuccesssublimcryptobackspacetonightbackspacemorningmorningnoticeshouldnoticefoundthetheshouldtheshouldfoundfoundcryptosuccessbackspacesuccessshouldweenternoticeweweshouldmorningfoundusersuccessbackspacewenoticeusersuccessenterenterexamplelearnfoundwetonightusercryptothesublimsublimtonightsuccesslearnbackspacetonightentertonightthesublimnoticewefoundcryptobackspaceenterenterlearnlearntonightexamplesystementersublimnoticecryptoshoulduseruserbackspaceuserwesublimmorningwesystemshouldtonighttheusershouldnoticefoundusernoticeentersublimwethewefoundfoundlearnfoundwecryptosystemexamplemorningcryptocryptosublimtheexamplenoticefoundlearnwelearnmorningtheenterthesystemsublimtonightsuccesssystemlearnshouldenterbackspaceentersuccesssuccessbackspaceexamplenoticeentershouldsublimlearnbackspacetheshouldexamplelearnsystemusersublimbackspacebackspacesuccesswelearntonightexamplewecryptoenterwesystemsystemsublimexamplecryptolearnmorningsublimfoundsublimfoundbackspacefoundtonighttonightnoticesuccesssuccessexampleusersuccesstonightsublimcryptosystemweenterexamplesystemthethenoticesublimtonightbackspacenoticesystemexamplethesuccesstonightmorningsuccesstonightwenoticesublimtonightwelearntonightmorningsublimbackspaceenterthetonightenterwecryptofoundtheenternoticebackspacesuccesswesystemuserexamplebackspaceentersuccesstonightsublimwemorningsuccesssuccesswesublimsuccessnoticesublimfoundlearnlearnweexamplecryptonoticelearnweusershoulduserfoundcryptolearnfoundmorningtonightmorningmorningnoticewecryptowewesuccessfoundsublimweuserentershouldshouldshouldsublimbackspacetonightenterwesublimsuccessshouldfoundthethetonightwecryptoweenterfoundcryptoshouldcryptouseruserfoundentersublimsublimthelearntheshouldnoticebackspacefoundsuccessshouldtonightentermorningsystemmorningtonightwenoticelearnbackspaceexampleusershouldnoticesublimsublimexamplethesuccessnoticesystemmorningnoticecryptosystemsublimcryptosystemsuccessshouldmorningbackspaceshouldmorninglearnnoticenoticeshouldthewewesublimsublimnoticeusersuccessentersystemfoundshouldshouldcryptobackspaceusermorningsystemshouldshouldtonightwesublimuserfoundlearnbackspacethetonightmorningexampleuserthefoundbackspaceshouldtonightcryptocryptofounduserexamplenoticecryptousernoticethenoticeshouldweshouldfoundwemorningcryptosuccesslearnfoundtonightsublimnoticenoticewefoundwewesuccesssublimsublimcryptoweexampletonightsuccessfoundshouldsuccesstonightbackspacesystemshouldwesystemnoticebackspaceusersystembackspacewenoticelearnnoticenoticesuccesslearntonightuserlearnsuccessbackspacesuccesswesystemusercryptonoticethesystemusernoticewethesuccessweshouldfoundshouldcryptomorningtonightwethewesuccesslearntheshouldweexampletonightsuccessnoticenoticemorningfoundmorningfoundusersublimsystemsuccessbackspacesuccessmorninguserthefoundweexamplemorningsublimlearnfoundfoundnoticemorningshouldweuserwemorningexamplesuccesssuccessfoundthetheshouldweusershouldtheshouldexamplenoticefoundsuccesssystemfoundshouldsublimbackspacetonightshouldsystemtonightsuccesslearntonightsystemsublimsuccesscryptobackspacesystemsublimmorningmorningshouldmorninglearnsuccesslearnmorningusermorninglearnexamplecryptoshouldbackspacesublimshouldfoundbackspacesystemsystemweexamplesystemtonightsublimmorningmorninguserfoundcryptolearnbackspaceshouldbackspacenoticesublimfoundthecryptousershouldsuccesssystemsuccessshouldsystembackspacesublimshouldsublimsystembackspaceexampleshouldbackspacesublimnoticelearnsublimuserbackspaceusersublimsuccesssublimuserusernoticeshouldsuccessnoticenoticelearnexamplesystemweexamplesublimbackspacebackspacecryptoshouldusercryptosublimbackspacesublimshouldsystemnoticenoticethesuccesssuccesslearnsystemsublimwenoticelearnusersublimsystemusernoticeuserthesuccesslearnwelearnwenoticecryptolearncryptonoticenoticebackspacecryptothecryptousercryptobackspacesuccesslearnthesystemsuccessthesystemsystemcryptosuccessbackspacesublimlearnsublimcryptobackspacelearnsublimusersublimexamplecryptosublimsystemnoticecryptocryptousertheusernoticebackspacenoticenoticethecryptocryptosystembackspacesublimbackspacecryptocryptobackspacesystemuserthenoticesystemsystemsystemusernoticethecryptouserusersystemtheusercryptoexamplenoticecryptoexamplenoticetheexampleexamplethecryptotheusernoticetheexampleexamplecryptotheexampleexamplethenoticethecryptocryptoexampletheexamplecryptocryptothenoticeexamplecryptonoticetheexampleexampleexamplecryptocryptoexampleexamplethenoticethecryptothethethethethetheexampleexamplethetheexampletheexampletheexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexampleexample

作詞頻分析，找出第4，8，11，15，16頻率高的詞出來。

data='''上面那串'''

statistics={}
frequency=[]
num=[4,8,11,15,16]
def zipin(lsit):
    for i in lsit:
        statistics.setdefault(data.count(i),str(i))
        frequency.append(data.count(i))
    frequency.sort()
    for i in num:
        print(statistics.get(frequency[i-1]),end='')
    print('\n')
    return(statistics)

if __name__ == '__main__':
    letters=["tonight","success","notice","example","should","crypto","backspace","learn","found","morning","we","system","sublim","the","user","enter"]
    print(zipin(letters))

程式運行結果

weshouldlearnthecrypto

{117: 'tonight', 138: 'success', 136: 'notice', 139: 'example', 131: 'should', 141: 'crypto', 129: 'backspace', 134: 'learn', 125: 'found', 113: 'morning', 124: 'we', 130: 'system', 132: 'sublim', 140: 'the', 133: 'user', 120: 'enter'}

[BJDCTF2020]easyrsa

題目給了一個檔案

from Crypto.Util.number import getPrime,bytes_to_long
from sympy import Derivative
from fractions import Fraction
from secret import flag

p=getPrime(1024)
q=getPrime(1024)
e=65537
n=p*q
z=Fraction(1,Derivative(arctan(p),p))-Fraction(1,Derivative(arth(q),q))
m=bytes_to_long(flag)
c=pow(m,e,n)
print(c,z,n)
'''
output:
7922547866857761459807491502654216283012776177789511549350672958101810281348402284098310147796549430689253803510994877420135537268549410652654479620858691324110367182025648788407041599943091386227543182157746202947099572389676084392706406084307657000104665696654409155006313203957292885743791715198781974205578654792123191584957665293208390453748369182333152809882312453359706147808198922916762773721726681588977103877454119043744889164529383188077499194932909643918696646876907327364751380953182517883134591810800848971719184808713694342985458103006676013451912221080252735948993692674899399826084848622145815461035
32115748677623209667471622872185275070257924766015020072805267359839059393284316595882933372289732127274076434587519333300142473010344694803885168557548801202495933226215437763329280242113556524498457559562872900811602056944423967403777623306961880757613246328729616643032628964072931272085866928045973799374711846825157781056965164178505232524245809179235607571567174228822561697888645968559343608375331988097157145264357626738141646556353500994924115875748198318036296898604097000938272195903056733565880150540275369239637793975923329598716003350308259321436752579291000355560431542229699759955141152914708362494482
15310745161336895413406690009324766200789179248896951942047235448901612351128459309145825547569298479821101249094161867207686537607047447968708758990950136380924747359052570549594098569970632854351825950729752563502284849263730127586382522703959893392329333760927637353052250274195821469023401443841395096410231843592101426591882573405934188675124326997277775238287928403743324297705151732524641213516306585297722190780088180705070359469719869343939106529204798285957516860774384001892777525916167743272419958572055332232056095979448155082465977781482598371994798871917514767508394730447974770329967681767625495394441

'''

首先可以依據程式碼推出z=p2+q2z=p^2+q^2，又有n=p∗qn=p*q，就可以依照(p+q)2=p2+2pq+q2(p+q)^2=p^2+2pq+q^2解出p和q。

from gmpy2 import *
from Crypto.Util.number import *

c = mpz(7922547866857761459807491502654216283012776177789511549350672958101810281348402284098310147796549430689253803510994877420135537268549410652654479620858691324110367182025648788407041599943091386227543182157746202947099572389676084392706406084307657000104665696654409155006313203957292885743791715198781974205578654792123191584957665293208390453748369182333152809882312453359706147808198922916762773721726681588977103877454119043744889164529383188077499194932909643918696646876907327364751380953182517883134591810800848971719184808713694342985458103006676013451912221080252735948993692674899399826084848622145815461035)
z = mpz(32115748677623209667471622872185275070257924766015020072805267359839059393284316595882933372289732127274076434587519333300142473010344694803885168557548801202495933226215437763329280242113556524498457559562872900811602056944423967403777623306961880757613246328729616643032628964072931272085866928045973799374711846825157781056965164178505232524245809179235607571567174228822561697888645968559343608375331988097157145264357626738141646556353500994924115875748198318036296898604097000938272195903056733565880150540275369239637793975923329598716003350308259321436752579291000355560431542229699759955141152914708362494482)
n = mpz(15310745161336895413406690009324766200789179248896951942047235448901612351128459309145825547569298479821101249094161867207686537607047447968708758990950136380924747359052570549594098569970632854351825950729752563502284849263730127586382522703959893392329333760927637353052250274195821469023401443841395096410231843592101426591882573405934188675124326997277775238287928403743324297705151732524641213516306585297722190780088180705070359469719869343939106529204798285957516860774384001892777525916167743272419958572055332232056095979448155082465977781482598371994798871917514767508394730447974770329967681767625495394441)
e = 65537

pqplus = iroot(z + 2 * n, 2)[0]
pqminus = iroot(z - 2 * n, 2)[0]
p = (pqplus + pqminus) // 2
q = (pqplus - pqminus) // 2

phi = (p - 1) * (q - 1)
d = invert(e, phi)
m = pow(c, d, n)

flag = long_to_bytes(m)
print(flag)

得到 b’BJD{Advanced_mathematics_is_too_hard!!!}’

yxx

題目給出明文和密文，用HxD開起來後可以轉為16進位，進行xor後取得真正的明文。

from gmpy2 import *
from Crypto.Util.number import *

m = 0x0A031702560115110A140E0A1E300E0A1E300E0A1E30140C190D1F100E060318
c = 0x6C6F76656C6F76656C6F76656C6F76656C6F76656C6F76656C6F76656C6F7665

m = m^c
flag = long_to_bytes(m)
print(flag)
b'flag:nctf{xor_xor_xor_biubiubiu}'

[AFCTF2018]Vigenère

密文看起來是詞頻分析，然後根據題目和程式碼判定是Vigenere。

解題網站

項目 結果
Key “csuwangjiang”
Key length 12
Cipher text length 6558
Ratio(cipher_len:key_len) 546.50
Difficulty easy
Clear text score (fitness) 101.57

解密出來的密文如下

When in the Course of human events it becomes necessary for one people to dissolve the political bands which have connected them with another and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, — That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn that mankind are more disposed to suffer, while evils are sufferable than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security. — Such has been the patient sufferance of these Colonies; and such is now the necessity which constrains them to alter their former Systems of Government. The history of the present King of Great Britain is a history of repeated injuries and usurpations, all having in direct object the establishment of an absolute Tyranny over these States. To prove this, let Facts be submitted to a candid world.

He has refused his Assent to Laws, the most wholesome and necessary for the public good.

He has forbidden his Governors to pass Laws of immediate and pressing importance, unless suspended in their operation till his Assent should be obtained; and when so suspended, he has utterly neglected to attend to them.

He has refused to pass other Laws for the accommodation of large districts of people, unless those people would relinquish the right of Representation in the Legislature, a right inestimable to them and formidable to tyrants only.

He has called together legislative bodies at places unusual, uncomfortable, and distant from the depository of their Public Records, for the sole purpose of fatiguing them into compliance with his measures.

He has dissolved Representative Houses repeatedly, for opposing with manly firmness his invasions on the rights of the people.

He has refused for a long time, after such dissolutions, to cause others to be elected, whereby the Legislative Powers, incapable of Annihilation, have returned to the People at large for their exercise; the State remaining in the mean time exposed to all the dangers of invasion from without, and convulsions within.

He has endeavoured to prevent the population of these States; for that purpose obstructing the Laws for Naturalization of Foreigners; refusing to pass others to encourage their migrations hither, and raising the conditions of new Appropriations of Lands.

He has obstructed the Administration of Justice by refusing his Assent to Laws for establishing Judiciary Powers.

He has made Judges dependent on his Will alone for the tenure of their offices, and the amount and payment of their salaries.

flag is afctf{Whooooooo_U_Gotcha!}

He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.

He has kept among us, in times of peace, Standing Armies without the Consent of our legislatures.

He has affected to render the Military independent of and superior to the Civil Power.

He has combined with others to subject us to a jurisdiction foreign to our constitution, and unacknowledged by our laws; giving his Assent to their Acts of pretended Legislation:

For quartering large bodies of armed troops among us:

For protecting them, by a mock Trial from punishment for any Murders which they should commit on the Inhabitants of these States:

For cutting off our Trade with all parts of the world:

For imposing Taxes on us without our Consent:

For depriving us in many cases, of the benefit of Trial by Jury:

For transporting us beyond Seas to be tried for pretended offences:

For abolishing the free System of English Laws in a neighbouring Province, establishing therein an Arbitrary government, and enlarging its Boundaries so as to render it at once an example and fit instrument for introducing the same absolute rule into these Colonies

For taking away our Charters, abolishing our most valuable Laws and altering fundamentally the Forms of our Governments:

For suspending our own Legislatures, and declaring themselves invested with power to legislate for us in all cases whatsoever.

He has abdicated Government here, by declaring us out of his Protection and waging War against us.

He has plundered our seas, ravaged our coasts, burnt our towns, and destroyed the lives of our people.

He is at this time transporting large Armies of foreign Mercenaries to compleat the works of death, desolation, and tyranny, already begun with circumstances of Cruelty & Perfidy scarcely paralleled in the most barbarous ages, and totally unworthy the Head of a civilized nation.

He has constrained our fellow Citizens taken Captive on the high Seas to bear Arms against their Country, to become the executioners of their friends and Brethren, or to fall themselves by their Hands.

He has excited domestic insurrections amongst us, and has endeavoured to bring on the inhabitants of our frontiers, the merciless Indian Savages whose known rule of warfare, is an undistinguished destruction of all ages, sexes and conditions.

In every stage of these Oppressions We have Petitioned for Redress in the most humble terms: Our repeated Petitions have been answered only by repeated injury. A Prince, whose character is thus marked by every act which may define a Tyrant, is unfit to be the ruler of a free people.

Nor have We been wanting in attentions to our British brethren. We have warned them from time to time of attempts by their legislature to extend an unwarrantable jurisdiction over us. We have reminded them of the circumstances of our emigration and settlement here. We have appealed to their native justice and magnanimity, and we have conjured them by the ties of our common kindred to disavow these usurpations, which would inevitably interrupt our connections and correspondence. They too have been deaf to the voice of justice and of consanguinity. We must, therefore, acquiesce in the necessity, which denounces our Separation, and hold them, as we hold the rest of mankind, Enemies in War, in Peace Friends.

We, therefore, the Representatives of the united States of America, in General Congress, Assembled, appealing to the Supreme Judge of the world for the rectitude of our intentions, do, in the Name, and by Authority of the good People of these Colonies, solemnly publish and declare, That these united Colonies are, and of Right ought to be Free and Independent States, that they are Absolved from all Allegiance to the British Crown, and that all political connection between them and the State of Great Britain, is and ought to be totally dissolved; and that as Free and Independent States, they have full Power to levy War, conclude Peace, contract Alliances, establish Commerce, and to do all other Acts and Things which Independent States may of right do. — And for the support of this Declaration, with a firm reliance on the protection of Divine Providence, we mutually pledge to each other our Lives, our Fortunes, and our sacred Honor.

根據眼力可以看到flag is afctf{Whooooooo_U_Gotcha!}解出此題。

[AFCTF2018]你能看出這是什麼加密麼

題目給了以下資訊

p = 0x928fb6aa9d813b6c3270131818a7c54edb18e3806942b88670106c1821e0326364194a8c49392849432b37632f0abe3f3c52e909b939c91c50e41a7b8cd00c67d6743b4f
q = 0xec301417ccdffa679a8dcc4027dd0d75baf9d441625ed8930472165717f4732884c33f25d4ee6a6c9ae6c44aedad039b0b72cf42cab7f80d32b74061
e = 0x10001
c = 0x70c9133e1647e95c3cb99bd998a9028b5bf492929725a9e8e6d2e277fa0f37205580b196e5f121a2e83bc80a8204c99f5036a07c8cf6f96c420369b4161d2654a7eccbdaf583204b645e137b3bd15c5ce865298416fd5831cba0d947113ed5be5426b708b89451934d11f9aed9085b48b729449e461ff0863552149b965e22b6

簡單看出是RSA，然後改一下前面的題目將flag取得。

from gmpy2 import *
from Crypto.Util.number import *

p = 0x928fb6aa9d813b6c3270131818a7c54edb18e3806942b88670106c1821e0326364194a8c49392849432b37632f0abe3f3c52e909b939c91c50e41a7b8cd00c67d6743b4f
q = 0xec301417ccdffa679a8dcc4027dd0d75baf9d441625ed8930472165717f4732884c33f25d4ee6a6c9ae6c44aedad039b0b72cf42cab7f80d32b74061
e = 0x10001
c = 0x70c9133e1647e95c3cb99bd998a9028b5bf492929725a9e8e6d2e277fa0f37205580b196e5f121a2e83bc80a8204c99f5036a07c8cf6f96c420369b4161d2654a7eccbdaf583204b645e137b3bd15c5ce865298416fd5831cba0d947113ed5be5426b708b89451934d11f9aed9085b48b729449e461ff0863552149b965e22b6

n = p * q
phi = (p - 1) * (q - 1)
d = invert(e, phi)
m = pow(c, d, n)

flag = long_to_bytes(m)
print(flag)

輸出

b'\x02\xd3\xe4v\xea\x80r\x83\xda\x99\x88\xf5#\x08\xbbAT\x8b\xaf\xd2\xf4\xdc\x9f\xd3\xbf\xb7A\xc3\xcc\xc5`\xa1\x8b\x86\x18y\xd0&\x88\x10\xef\xbe\x83\xcer\xceC\x17\xec[\xb7%\x08\xef\x16\x1f\xab\x0c\x96\xa3\xdc N^\x8e,\xa3\x11{\x99U\xcd\x15o\xd7B\xf4L\x8f}&\xc5$\xca\xd5;\xf9\x02Y\xc1\xbbS\xfd4\x83M\x96\xa9\xbd;\x83/\xf7\x00afctf{R54_|5_$0_$imp13}'

afctf{R54_|5_0_imp13}

[AFCTF2018]可憐的RSA

題目給出一組公鑰和加密後的flag，先依據公鑰拆出n和e的值。

from Crypto.PublicKey import RSA

c = '''-----BEGIN PUBLIC KEY-----
MIIBJDANBgkqhkiG9w0BAQEFAAOCAREAMIIBDAKCAQMlsYv184kJfRcjeGa7Uc/4
3pIkU3SevEA7CZXJfA44bUbBYcrf93xphg2uR5HCFM+Eh6qqnybpIKl3g0kGA4rv
tcMIJ9/PP8npdpVE+U4Hzf4IcgOaOmJiEWZ4smH7LWudMlOekqFTs2dWKbqzlC59
NeMPfu9avxxQ15fQzIjhvcz9GhLqb373XDcn298ueA80KK6Pek+3qJ8YSjZQMrFT
+EJehFdQ6yt6vALcFc4CB1B6qVCGO7hICngCjdYpeZRNbGM/r6ED5Nsozof1oMbt
Si8mZEJ/Vlx3gathkUVtlxx/+jlScjdM7AFV5fkRidt0LkwosDoPoRz/sDFz0qTM
5q5TAgMBAAE=
-----END PUBLIC KEY-----'''

key = RSA.import_key(c)

print('e = %d' % key.e)
print('n = %d' % key.n)

輸出

e = 65537
n = 79832181757332818552764610761349592984614744432279135328398999801627880283610900361281249973175805069916210179560506497075132524902086881120372213626641879468491936860976686933630869673826972619938321951599146744807653301076026577949579618331502776303983485566046485431039541708467141408260220098592761245010678592347501894176269580510459729633673468068467144199744563731826362102608811033400887813754780282628099443490170016087838606998017490456601315802448567772411623826281747245660954245413781519794295336197555688543537992197142258053220453757666537840276416475602759374950715283890232230741542737319569819793988431443

再透過分解n得到p和q。

p = 3133337 
q = 25478326064937419292200172136399497719081842914528228316455906211693118321971399936004729134841162974144246271486439695786036588117424611881955950996219646807378822278285638261582099108339438949573034101215141156156408742843820048066830863814362379885720395082318462850002901605689761876319151147352730090957556940842144299887394678743607766937828094478336401159449035878306853716216548374273462386508307367713112073004011383418967894930554067582453248981022011922883374442736848045920676341361871231787163441467533076890081721882179369168787287724769642665399992556052144845878600126283968890273067575342061776244939

接下來就可以透過RSA套件爆開。

from gmpy2 import *
from Crypto.Util.number import *
from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP
import base64

e = 65537
n = 79832181757332818552764610761349592984614744432279135328398999801627880283610900361281249973175805069916210179560506497075132524902086881120372213626641879468491936860976686933630869673826972619938321951599146744807653301076026577949579618331502776303983485566046485431039541708467141408260220098592761245010678592347501894176269580510459729633673468068467144199744563731826362102608811033400887813754780282628099443490170016087838606998017490456601315802448567772411623826281747245660954245413781519794295336197555688543537992197142258053220453757666537840276416475602759374950715283890232230741542737319569819793988431443
p = 3133337
q = 25478326064937419292200172136399497719081842914528228316455906211693118321971399936004729134841162974144246271486439695786036588117424611881955950996219646807378822278285638261582099108339438949573034101215141156156408742843820048066830863814362379885720395082318462850002901605689761876319151147352730090957556940842144299887394678743607766937828094478336401159449035878306853716216548374273462386508307367713112073004011383418967894930554067582453248981022011922883374442736848045920676341361871231787163441467533076890081721882179369168787287724769642665399992556052144845878600126283968890273067575342061776244939

phi = (p - 1) * (q - 1)
d = invert(e, phi)

c = 'GVd1d3viIXFfcHapEYuo5fAvIiUS83adrtMW/MgPwxVBSl46joFCQ1plcnlDGfL19K/3PvChV6n5QGohzfVyz2Z5GdTlaknxvHDUGf5HCukokyPwK/1EYU7NzrhGE7J5jPdi0Aj7xi/Odxy0hGMgpaBLd/nL3N8O6i9pc4Gg3O8soOlciBG/6/xdfN3SzSStMYIN8nfZZMSq3xDDvz4YB7TcTBh4ik4wYhuC77gmT+HWOv5gLTNQ3EkZs5N3EAopy11zHNYU80yv1jtFGcluNPyXYttU5qU33jcp0Wuznac+t+AZHeSQy5vk8DyWorSGMiS+J4KNqSVlDs12EqXEqqJ0uA=='

c_bytes = base64.b64decode(c)
rsa_components = (n, e, int(d), p, q)
arsa = RSA.construct(rsa_components)
rsakey = RSA.importKey(arsa.exportKey())
rsakey = PKCS1_OAEP.new(rsakey)
decrypted = rsakey.decrypt(c_bytes)
print(decrypted)

輸出

b'afctf{R54_|5_$0_B0rin9}'

[網鼎杯2020 青龍組]boom

題目給了一個boom.exe，在終端打開後可以看到

Na Na Na Na



                @@@@@@@@@           @@@@@@@@@
            @@@@@@@@@@@@@@@@@   @@@@@@@@@@@@@@@@@
           @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
         @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
        @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
        @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
        @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
        @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
        @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
        @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
         @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
          @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
           @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
            @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
             @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
              @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
                @@@@@@@@@@@@@@@@@@@@@@@@@@@@@
                  @@@@@@@@@@@@@@@@@@@@@@@@@
                    @@@@@@@@@@@@@@@@@@@@@
                       @@@@@@@@@@@@@@@
                          @@@@@@@@@
                             @@@





Play a simple game
請按任意鍵繼續 . . .

繼續後得到下一步的資訊

first:this string md5:46e5efe6165a5afb361217446a2dbd01

都提示是md5了，也沒什麼特別的內容，解出是en5oy之後丟進去得到下一個題目。

first:this string md5:46e5efe6165a5afb361217446a2dbd01
en5oy
Great next level
請按任意鍵繼續 . . .

接下來是解聯立方程，輸入x, y, z後進入下一階段。

This time:Here are have some formulas
3x-y+z=185
2x+3y-z=321
x+y+z=173
input: x = 74
input: y = 68
input : z = 31

此問題可以先用求根找出解，發現7943722218936282=89127561∗891275617943722218936282 = 89127561 * 89127561，結束取得flag。

Last time: Kill it
x*x+x-7943722218936282=0
input x: 89127561
Great This is your FLAG
flag{en5oy_746831_89127561}

感覺比較像是misc，不知道為什麼放錯分類了。

[RoarCTF2019]babyRSA

題目如下

import sympy
import random

def myGetPrime():
    A= getPrime(513)
    print(A)
    B=A-random.randint(1e3,1e5)
    print(B)
    return sympy.nextPrime((B!)%A)
p=myGetPrime()
#A1=21856963452461630437348278434191434000066076750419027493852463513469865262064340836613831066602300959772632397773487317560339056658299954464169264467234407
#B1=21856963452461630437348278434191434000066076750419027493852463513469865262064340836613831066602300959772632397773487317560339056658299954464169264467140596

q=myGetPrime()
#A2=16466113115839228119767887899308820025749260933863446888224167169857612178664139545726340867406790754560227516013796269941438076818194617030304851858418927
#B2=16466113115839228119767887899308820025749260933863446888224167169857612178664139545726340867406790754560227516013796269941438076818194617030304851858351026

r=myGetPrime()

n=p*q*r
#n=85492663786275292159831603391083876175149354309327673008716627650718160585639723100793347534649628330416631255660901307533909900431413447524262332232659153047067908693481947121069070451562822417357656432171870951184673132554213690123308042697361969986360375060954702920656364144154145812838558365334172935931441424096270206140691814662318562696925767991937369782627908408239087358033165410020690152067715711112732252038588432896758405898709010342467882264362733
c=pow(flag,e,n)
#e=0x1001
#c=75700883021669577739329316795450706204502635802310731477156998834710820770245219468703245302009998932067080383977560299708060476222089630209972629755965140317526034680452483360917378812244365884527186056341888615564335560765053550155758362271622330017433403027261127561225585912484777829588501213961110690451987625502701331485141639684356427316905122995759825241133872734362716041819819948645662803292418802204430874521342108413623635150475963121220095236776428
#so,what is the flag?

關鍵處應該是

return sympy.nextPrime((B!)%A)

可以拆出

p=(B1!) mod A1\n q=(B2!) mod A2

正常來說(B!) mod A基本上是算不出來的，我找了一下發現了威爾遜定理，他的定理如下，想看充分性與必要性證明的自己查Wiki。

若且唯若p為質數時，(p−1)!≡−1(modp)(p-1)!≡-1(mod p)

看起來應該是可以透過A和B的相似性來對公式做變形，但之後就沒有頭緒了，嘗試著找了網路上的解答，但看不太懂，希望以後自己可以解出來。

[NCTF2019]babyRSA

題目給定如下

from Crypto.Util.number import *
from flag import flag

def nextPrime(n):
    n += 2 if n & 1 else 1
    while not isPrime(n):
        n += 2
    return n

p = getPrime(1024)
q = nextPrime(p)
n = p * q
e = 0x10001
d = inverse(e, (p-1) * (q-1))
c = pow(bytes_to_long(flag.encode()), e, n)

# d = 19275778946037899718035455438175509175723911466127462154506916564101519923603308900331427601983476886255849200332374081996442976307058597390881168155862238533018621944733299208108185814179466844504468163200369996564265921022888670062554504758512453217434777820468049494313818291727050400752551716550403647148197148884408264686846693842118387217753516963449753809860354047619256787869400297858568139700396567519469825398575103885487624463424429913017729585620877168171603444111464692841379661112075123399343270610272287865200880398193573260848268633461983435015031227070217852728240847398084414687146397303110709214913
# c = 5382723168073828110696168558294206681757991149022777821127563301413483223874527233300721180839298617076705685041174247415826157096583055069337393987892262764211225227035880754417457056723909135525244957935906902665679777101130111392780237502928656225705262431431953003520093932924375902111280077255205118217436744112064069429678632923259898627997145803892753989255615273140300021040654505901442787810653626524305706316663169341797205752938755590056568986738227803487467274114398257187962140796551136220532809687606867385639367743705527511680719955380746377631156468689844150878381460560990755652899449340045313521804

透過(e∗d−1)(e*d-1)%((p-1)(q-1))=0進行爆破，得到phi，也就是(p-1)(q-1)，因為p, q差異不大，對phi開根號就可以求出p, q。

from Crypto.Util.number import *
import sympy.crypto

e = 0x10001
d = 19275778946037899718035455438175509175723911466127462154506916564101519923603308900331427601983476886255849200332374081996442976307058597390881168155862238533018621944733299208108185814179466844504468163200369996564265921022888670062554504758512453217434777820468049494313818291727050400752551716550403647148197148884408264686846693842118387217753516963449753809860354047619256787869400297858568139700396567519469825398575103885487624463424429913017729585620877168171603444111464692841379661112075123399343270610272287865200880398193573260848268633461983435015031227070217852728240847398084414687146397303110709214913
c = 5382723168073828110696168558294206681757991149022777821127563301413483223874527233300721180839298617076705685041174247415826157096583055069337393987892262764211225227035880754417457056723909135525244957935906902665679777101130111392780237502928656225705262431431953003520093932924375902111280077255205118217436744112064069429678632923259898627997145803892753989255615273140300021040654505901442787810653626524305706316663169341797205752938755590056568986738227803487467274114398257187962140796551136220532809687606867385639367743705527511680719955380746377631156468689844150878381460560990755652899449340045313521804

ed1 = e * d - 1
p = 0
q = 0

for k in range(pow(2, 15), pow(2, 16)):
    if ed1 % k == 0:
        p = sympy.prevprime(gmpy2.iroot(ed1 // k, 2)[0])
        q = sympy.nextprime(p)
        if (p - 1) * (q - 1) * k == ed1:
            break

n = p * q
m = pow(c, d, n)
flag = long_to_bytes(m)

print(flag)

輸出

b'NCTF{70u2_nn47h_14_v3ry_gOO0000000d}'

[RoarCTF2019]RSA

題目給定如下

A=(((y%x)**5)%(x%y))**2019+y**316+(y+1)/x
p=next_prime(z*x*y)
q=next_prime(z)
A =  2683349182678714524247469512793476009861014781004924905484127480308161377768192868061561886577048646432382128960881487463427414176114486885830693959404989743229103516924432512724195654425703453612710310587164417035878308390676612592848750287387318129424195208623440294647817367740878211949147526287091298307480502897462279102572556822231669438279317474828479089719046386411971105448723910594710418093977044179949800373224354729179833393219827789389078869290217569511230868967647963089430594258815146362187250855166897553056073744582946148472068334167445499314471518357535261186318756327890016183228412253724
n =  117930806043507374325982291823027285148807239117987369609583515353889814856088099671454394340816761242974462268435911765045576377767711593100416932019831889059333166946263184861287975722954992219766493089630810876984781113645362450398009234556085330943125568377741065242183073882558834603430862598066786475299918395341014877416901185392905676043795425126968745185649565106322336954427505104906770493155723995382318346714944184577894150229037758434597242564815299174950147754426950251419204917376517360505024549691723683358170823416757973059354784142601436519500811159036795034676360028928301979780528294114933347127
c =  41971850275428383625653350824107291609587853887037624239544762751558838294718672159979929266922528917912189124713273673948051464226519605803745171340724343705832198554680196798623263806617998072496026019940476324971696928551159371970207365741517064295956376809297272541800647747885170905737868568000101029143923792003486793278197051326716680212726111099439262589341050943913401067673851885114314709706016622157285023272496793595281054074260451116213815934843317894898883215362289599366101018081513215120728297131352439066930452281829446586562062242527329672575620261776042653626411730955819001674118193293313612128

依照慣例，n可以透過factordb分解成p和q。

p = 842868045681390934539739959201847552284980179958879667933078453950968566151662147267006293571765463137270594151138695778
986165111380428806545593588078365331313084230014618714412959584843421586674162688321942889369912392031882620994944241987
153078156389470370195514285850736541078623854327959382156753458569
q = 139916095583110895133596833227506693679306709873174024876891023355860781981175916446323044732913066880786918629089023499
311703408489151181886568535621008644997971982182426706592551291084007983387911006261442519635405457077292515085160744169
867410973960652081452455371451222265819051559818441257438021073941183

解密所需要的c, d, n只剩下c沒有辦法找出來，使用爆破的方式來做。

from gmpy2 import *
from Crypto.Util.number import *

n = 117930806043507374325982291823027285148807239117987369609583515353889814856088099671454394340816761242974462268435911765045576377767711593100416932019831889059333166946263184861287975722954992219766493089630810876984781113645362450398009234556085330943125568377741065242183073882558834603430862598066786475299918395341014877416901185392905676043795425126968745185649565106322336954427505104906770493155723995382318346714944184577894150229037758434597242564815299174950147754426950251419204917376517360505024549691723683358170823416757973059354784142601436519500811159036795034676360028928301979780528294114933347127
c = 41971850275428383625653350824107291609587853887037624239544762751558838294718672159979929266922528917912189124713273673948051464226519605803745171340724343705832198554680196798623263806617998072496026019940476324971696928551159371970207365741517064295956376809297272541800647747885170905737868568000101029143923792003486793278197051326716680212726111099439262589341050943913401067673851885114314709706016622157285023272496793595281054074260451116213815934843317894898883215362289599366101018081513215120728297131352439066930452281829446586562062242527329672575620261776042653626411730955819001674118193293313612128

p = 139916095583110895133596833227506693679306709873174024876891023355860781981175916446323044732913066880786918629089023499311703408489151181886568535621008644997971982182426706592551291084007983387911006261442519635405457077292515085160744169867410973960652081452455371451222265819051559818441257438021073941183
q = 842868045681390934539739959201847552284980179958879667933078453950968566151662147267006293571765463137270594151138695778986165111380428806545593588078365331313084230014618714412959584843421586674162688321942889369912392031882620994944241987153078156389470370195514285850736541078623854327959382156753458569
phi = (p - 1) * (q - 1)

for e in range(2, 100000):
    try:
        if isPrime(e):
            d = invert(e, phi)
            flag = long_to_bytes(pow(c, d, n))
            flag = str(flag)
            if "CTF{" in flag:
                print('e =', e)
                print(flag)
    except ZeroDivisionError:
        continue

輸出

e = 65537 
b'RoarCTF{wm-l1l1ll1l1l1l111ll}'

[AFCTF2018]Single

題目給了兩個檔案，一個是密文，一個是Encode.cpp。

#include <bits/stdc++.h>
using namespace std;
int main()
{
	freopen("Plain.txt","r",stdin);
	freopen("Cipher.txt","w",stdout);
	map<char, char> f;
	int arr[26];
	for(int i=0;i<26;++i){
		arr[i]=i;
	}
	random_shuffle(arr,arr+26);
	for(int i=0;i<26;++i){
		f['a'+i]='a'+arr[i];
		f['A'+i]='A'+arr[i];
	}
	char ch;
	while((ch=getchar())!=EOF){
		if(f.count(ch)){
			putchar(f[ch]);
		}else{
			putchar(ch);
		}
	}
	return 0;
}
Jmqrida rva Lfmz (JRL) eu m uqajemf seny xl enlxdomrexn uajiderc jxoqarerexnu. Rvada mda rvdaa jxooxn rcqau xl JRLu: Paxqmdyc, Mrrmjs-Yalanja mny oekay.

Paxqmdyc-urcfa JRLu vmu m jxiqfa xl giaurexnu (rmusu) en dmnza xl jmrazxdeau. Lxd akmoqfa, Wab, Lxdanuej, Jdcqrx, Benmdc xd uxoarvenz afua. Ramo jmn zmen uxoa qxenru lxd atadc uxftay rmus. Oxda qxenru lxd oxda jxoqfejmray rmusu iuimffc. 

Rva nakr rmus en jvmen jmn ba xqanay xnfc mlrad uxoa ramo uxfta qdatexiu rmus. Rvan rva zmoa reoa eu xtad uio xl qxenru uvxwu cxi m JRL wenad. Lmoxiu akmoqfa xl uijv JRL eu Yaljxn JRL gimfu.

Waff, mrrmjs-yalanja eu mnxrvad enradaurenz seny xl jxoqarerexnu. Vada atadc ramo vmu xwn narwxds(xd xnfc xna vxur) werv tifnmdmbfa uadtejau. Cxid ramo vmu reoa lxd qmrjvenz cxid uadtejau mny yatafxqenz akqfxeru iuimffc. Ux, rvan xdzmnehadu jxnnajru qmdrejeqmnru xl jxoqarerexn mny rva wmdzmoa urmdru! Cxi uvxify qdxrajr xwn uadtejau lxd yalanja qxenru mny vmjs xqqxnanru lxd mrrmjs qxenru. 

Veurxdejmffc rveu eu m ledur rcqa xl JRLu, atadcbxyc snxwu mbxir YAL JXN JRL - uxoarvenz fesa m Wxdfy Jiq xl mff xrvad jxoqarerexnu.Oekay jxoqarerexnu omc tmdc qxuuebfa lxdomru. Er omc ba uxoarvenz fesa wmdzmoa werv uqajemf reoa lxd rmus-bmuay afaoanru (a.z. IJUB eJRL).

JRL zmoau xlran rxijv xn omnc xrvad muqajru xl enlxdomrexn uajiderc: jdcqrxzdmqvc, urazx, benmdc mnmfcueu, datadua anzanaadenz, oxbefa uajiderc mny xrvadu. Zxxy ramou zanadmffc vmta urdxnz useffu mny akqadeanja en mff rvaua euuiau.

Iuimffc, lfmz eu uxoa urdenz xl dmnyxo ymrm xd rakr en uxoa lxdomr. 

Akmoqfa mljrl{Xv_I_lxiny_er_neja_rDc}

詞頻分析直接丟 https://quipqiup.com/，把原文翻譯出來。

Vhecowis hmwbwjeny dwv hcjvr saeys. Srbkeh Kwevwb.Capture the Flag (CTF) is a special kind of information security competitions. There are three common types of CTFs: Jeopardy, Attack-Defence and mixed. 

Jeopardy-style CTFs has a couple of questions (tasks) in range of categories. For example, Web, Forensic, Crypto, Binary or something else. Team can gain some points for every solved task. More points for more complicated tasks usually. 

The next task in chain can be opened only after some team solve previous task. Then the game time is over sum of points shows you a CTF winer. Famous example of such CTF is Defcon CTF quals. 

Well, attack-defence is another interesting kind of competitions. Here every team has own network(or only one host) with vulnarable services. Your team has time for patching your services and developing exploits usually. So, then organizers connects participants of competition and the wargame starts! You should protect own services for defence points and hack opponents for attack points. 

Historically this is a first type of CTFs, everybody knows about DEF CON CTF - something like a World Cup of all other competitions. Mixed competitions may vary possible formats. It may be something like wargame with special time for task-based elements (e.g. UCSB iCTF). 

CTF games often touch on many other aspects of information security: cryptography, stego, binary analysis, reverse engeneering, mobile security and others. Good teams generally have strong skills and experience in all these issues. Usually, flag is some string of random data or text in some format.

Example afctf{Oh_U_found_it_nice_tRy}

[BJDCTF2020]signin

題目如下

424a447b57653163306d655f74345f424a444354467d

看起來是hex，轉成base64之後，發現還是亂碼，改轉成ascii之後得到flag。

BJD{We1c0me_t4_BJDCTF}

[MRCTF2020]vigenere

密文

g vjganxsymda ux ylt vtvjttajwsgt bl udfteyhfgt
oe btlc ckjwc qnxdta 
vbbwwrbrtlx su gnw nrshylwmpy cgwps, lum bipee ynecgy gk jaryz frs fzwjp, x puej jgbs udfteyhfgt, gnw sil uuej su zofi. sc okzfpu bl lmi uhzmwi, x nyc dsj bl lmi enyl ys argnj yh nrgsi. nba swi cbz ojprbsw fqdam mx. cdh nsai cb ygaigroysxn jnwwi lr msylte.
cw mekr tg jptpzwi kdikjsqtaz, ftv pek oj pxxkdd xd ugnj scr, yg n esqxwxw nba onxw au ywipgkj fyiuujnxn gnss xwnz onxw jnahl avhwwxn vzkjpu nrofch fvwfoh. v jwhppek lmi vyutfp hbiafp hcguj at nxw gyxyjask ib hw seihxsqpn vtvjttajwsx ds zzj xnegfsmtf egz wtrq lt mbcukj sc hy. qty wnbw ss bbxsq vxtnl ys ghrw zw cbx vt cdh vgxwtfy ssc brzzthh bl wsjdeiwricg cw mekr zjzi grgktr ib lwfv.
vbbwwrbrtlx hteonj xwroj oyhg vgbigf ljtq iuk utrhrtl tj iuk ytztetwi. cdh nsai crolmig fudngxgkv ssg ekujmkrj gzvh. jk vnh cbz aszxgk qty. nba vt rdg qfta jf, tgw hd lum prdj umw aderv. hcqrxkuerr jgjw cbz dni lvzznr nbaj gsgqkjx. hd aul ylxaq lmei lum hec oaaqh xg, gk yldhmz nx lrxw f tjorah gdaylwyrgogs tgbpwhx. nba ufrcbz. ay mh nt shx ds tsyygr gfi mi txgbw xgywqj iuxgzkw baj hsaykuymkr guymday.
qty wnbw ssi rtyfktq of tyg txwfx paj yfxwrxask rbtnjvhnzatr, cbx vnh nba uwipgk lmi lrgdyl ds umw qpeqwytaniwx. cdh jg ssi xtgb sje imqxjek, gzv tgnahw, de zzj ycjxayxta igiih gnsy eaeksic eeunnht baj xsrvkld qdek gwhte zzfr rbadi ft bhlfmcrj td ecl ux dsje oeushvzatrh.
lum hppvs lmigr gjj tgbhdjqh nsgsk jf zzfx nba fjis gu ktpkr. egz yhr zznw rygar eh nt wcgjfk lt mcigvj sje vjjgxailx. qpae gk xwryw uvdorwrw sbt'l jbxfz. omigr zzjvt nxw wipy igsjavilx, awrxw yltek swi leuflw, lr caqp xqkfymul zzjq paj sihgryk yltz hq tyg zkssw. lr gjj jdesask dhx gbr hbiafp rbtlwerg. zznw vbbwwrpaiw bmay gjnwt niutvsvty ys iuk utrsvzatrh bl gzv lbxdi, rdg egzvh. baj bsgyj ax hxslwwicg.
iqgigfvshi rbtknwif ux yvpayshxxbtk, wianzatrhuohx, ecq zztyvuz aywtyl, swvplkv qmzr g kyecqofl apik as xwr cwg su baj hsbzafngpgogsw. dhxk nw p jujqh iugl nw qbzz jzteeomigr gfi rdjnwwi, qhz ay mh aul bltek tthxry dnzt.
jk swi reksymct g otvaq zzfx pyr efc tazww axgngzx eeonnpttk gw tgrpmimrr guhsgqkv gc gniw, jgdaueng ebcww, qxyolfvn sujhi, de ylfxxbt gk fxezz.
bi pek uwipgofl e lbxdi awrxw frnbtw, frnjnwwi bne wctgryk mmh bx zjv qrrajjh, au efxirx zta hvtyzppe, cayldhz xjeg bl tjmct igjvrrj asxd fodjrrr uj hscsujrmil.
egzv armsq gdaiwuxh bl hwserxld, imcxwxwxbt, aiicgold, qdikejri, ntv hscgkpy hd aul fteye lt yh. gnwd egr gdq fpfkv tr bnzljv, paj lmigr ok ss bnzljv wrxw.
tyg vjwsxxgowx lpik ft fdqowx, wd, htdnot lum, bi rntftx dozsnr dejww fn cnqxmrnr utigpogs. at okdnikr zzfx ueue jxwvik, jravmzyicrj kjpu-vtljvtfz, ssh iuk utqbbtojea, baj lskrxffrrr caqp tzkjli. dhx aiicgolnih zgq gi svylwmqhzwi ereukx qpae gk cdhx bzvxfjahxxbtk. ylt btdd ppj zzfx pyr gzv rbtkymihkfy gjyzmwih jumqh vrtwweaye jjgdttaei xf zzj kdyjws vjyk. oj ldck oj axyr tj eqyk lt fjvrv tyg cgjymrhrsw wdyalnscf uf ylpg hsxmh. oal bi rntftx ppiwux iuk ktpjgogsw nba swi pgzwrtivty ys xzvgxi.
xa zzj ycvzwi winzwx, cdh nsai ibjsd ggrgljh p ygo, ylt gkdjgdzsmsmrnzatrh ekxtvb nil, blxpn jjtjqosyih lumw sla igswivzmymda gfi mcfadyw iuk vwipzy gk ntslwwwda, csxlxamltr, bvrd, resvygs, htguizikvrdj, ecq hjfrsrok. yltfk vwipzy ezwi auo gi qbxf frtj of zw.
nba swi irxjnjxrj gk cdhx gbr ruodivta, yasgt gnwd egr tsymkry as e lbxdi awrxw dsj jodq eajgqx ft vsenkgntlx. ftpgmxi nba xjeg gnwr, cdh kfyvjfz qtyg oajjejpxshmtf cayl iuk hfvtazsq vtfvgswxoodnxxry qty pek lts rbcswhal zg hscsxgsx nbajxiaikk. nr dhx otvaq, gdq xwr ywsxxzkfyw paj wctgryknscf ux mybntayc, ueue ylt qktfwxam lt xwr gfliavi, swi enxlx su n ywfqaryk bldyk, lmi vyutfp rbtnjvhnzatr ds hayw. lr issrdg ywuegnzw ylt noj ylpg iztotf ljtq iuk snv jcuf blxpn onrvf hwfx.
xa iznrp, tkjrecl, ljfrrr, xmxwxn, yaskpcujj, minrq frs gnw zrxgkv xxpgkk, dsj nxw yvnvty ys lnxv tju gnw amghy gk pxokjyc ql kjjgivty lypej htwif gl ylt sxgsxxrxk tj rlhwwweniw. yltfk efc zrkh tyi gnw hscggynsc suj f wbnrd ymbr, hmy xwre onpa aul bsgx of f aderv ylpg caqp hbuf gi qygfpiirj as fxg-hwfvxam ejhxn.
egzv xaijjehvtyqc doygqiir ofksgzglnsc vtvzwieowx adhrv uigcklzeir zzjqhrrnjw ql vjttdfofl ppjy, as ebrxahe paj wqwtjnwwi, iugl hppvs lt sla yhjiru olxias zzwsjtngzx iuk otvaq. zzjwt ygox adhrv iirygjj msrgk ys qr gftxwrx ashjfzjnea cxgiyrg, tg rsgr tggpt gnss txt ojtr. xa umw aderv, blpgknjv iuk zzqpa sash bne uwipgk ufr qr xwuvdqaujh paj vnwieotzxtq ofkmcvzwqc pg tg hshg. zzj kabhsq gdabwdecpk gk xwbaymx cb rgskte xwvyxekk dsje lshxdeowx xd niutqeyokm.
xwryw nrreksxmctrq mshgodj ecq igqscvgd ripfajjw eyguj yh vt lmi hnsw ushvzatr pf zztwt cxwamdhy dtztey gk jgrkvtq paj kjpu-qkljvbvtsymda czt lpq zg wiyril ylt nalmsgvzajw ds jaxxpaz, msmcsujris cuojvh. jk ezwi qkuqegr umw zxezmfp hrrnjw xzsmsi ib egzv hbbwwixttld, ikrt sx at pufymchk lt gdaywsx ib egzv ghrw tzte umw fdqowx. at jodq weeksi sjeywqztf guwshf zzj tantwy wd gnsy rd btw hec nxjjwi baj yldhmzyw.
lr caqp reksyi p ponnpxmglnsc bl lmi bvtv nr rlhwwweniw. ren vz tj qdek zzqpak ssh unoj ylpa zzj aderv dsje mgaigaswsxh ugnj qpqk tjjdek.
xqev vy ewgis balicrxw hvnczg hvppq efr, eyksxi pqj mshteyutvt ntv hygye twerry.

根據加密方式看出是vigenere之後，丟進 https://guballa.de/vigenere-solver 之後得到原文，key是gsfepn。

a declaration of the independence of cyberspace
by john perry barlow 
governments of the industrial world, you weary giants of flesh and steel, i come from cyberspace, the new home of mind. on behalf of the future, i ask you of the past to leave us alone. you are not welcome among us. you have no sovereignty where we gather.
we have no elected government, nor are we likely to have one, so i address you with no greater authority than that with which liberty itself always speaks. i declare the global social space we are building to be naturally independent of the tyrannies you seek to impose on us. you have no moral right to rule us nor do you possess any methods of enforcement we have true reason to fear.
governments derive their just powers from the consent of the governed. you have neither solicited nor received ours. we did not invite you. you do not know us, nor do you know our world. cyberspace does not lie within your borders. do not think that you can build it, as though it were a public construction project. you cannot. it is an act of nature and it grows itself through our collective actions.
you have not engaged in our great and gathering conversation, nor did you create the wealth of our marketplaces. you do not know our culture, our ethics, or the unwritten codes that already provide our society more order than could be obtained by any of your impositions.
you claim there are problems among us that you need to solve. you use this claim as an excuse to invade our precincts. many of these problems don't exist. where there are real conflicts, where there are wrongs, we will identify them and address them by our means. we are forming our own social contract. this governance will arise according to the conditions of our world, not yours. our world is different.
cyberspace consists of transactions, relationships, and thought itself, arrayed like a standing wave in the web of our communications. ours is a world that is both everywhere and nowhere, but it is not where bodies live.
we are creating a world that all may enter without privilege or prejudice accorded by race, economic power, military force, or station of birth.
we are creating a world where anyone, anywhere may express his or her beliefs, no matter how singular, without fear of being coerced into silence or conformity.
your legal concepts of property, expression, identity, movement, and context do not apply to us. they are all based on matter, and there is no matter here.
our identities have no bodies, so, unlike you, we cannot obtain order by physical coercion. we believe that from ethics, enlightened self-interest, and the commonweal, our governance will emerge. our identities may be distributed across many of your jurisdictions. the only law that all our constituent cultures would generally recognize is the golden rule. we hope we will be able to build our particular solutions on that basis. but we cannot accept the solutions you are attempting to impose.
in the united states, you have today created a law, the telecommunications reform act, which repudiates your own constitution and insults the dreams of jefferson, washington, mill, madison, detoqueville, and brandeis. these dreams must now be born anew in us.
you are terrified of your own children, since they are natives in a world where you will always be immigrants. because you fear them, you entrust your bureaucracies with the parental responsibilities you are too cowardly to confront yourselves. in our world, all the sentiments and expressions of humanity, from the debasing to the angelic, are parts of a seamless whole, the global conversation of bits. we cannot separate the air that chokes from the air upon which wings beat.
in china, germany, france, russia, singapore, italy and the united states, you are trying to ward off the virus of liberty by erecting guard posts at the frontiers of cyberspace. these may keep out the contagion for a small time, but they will not work in a world that will soon be blanketed in bit-bearing media.
your increasingly obsolete information industries would perpetuate themselves by proposing laws, in america and elsewhere, that claim to own speech itself throughout the world. these laws would declare ideas to be another industrial product, no more noble than pig iron. in our world, whatever the human mind may create can be reproduced and distributed infinitely at no cost. the global conveyance of thought no longer requires your factories to accomplish.
these increasingly hostile and colonial measures place us in the same position as those previous lovers of freedom and self-determination who had to reject the authorities of distant, uninformed powers. we must declare our virtual selves immune to your sovereignty, even as we continue to consent to your rule over our bodies. we will spread ourselves across the planet so that no one can arrest our thoughts.
we will create a civilization of the mind in cyberspace. may it be more humane and fair than the world your governments have made before.
flag is mrctf vigenere crypto crack man, please add underscore and curly braces.

關鍵句是flag is mrctf vigenere crypto crack man，開始嘗試提交，flag{vigenere_crypto_crack_man}就是答案了。

[MRCTF2020]keyboard

題目如下

得到的flag用
MRCTF{xxxxxx}形式上叫
都为小写字母

6
666
22
444
555
33
7
44
666
66
3

先用鍵盤打打看，沒有頭緒，後來想到手機簡訊按鍵，就打開手機對照，打出mobilephond，提交失敗後查詢一下，發現應該是mobile phone，就成功了。

flag{mobilephone}