题目: [了不起的盖茨比]
时间: 2023-05-23
难度: 2
tags: [CTF,Crypto]
题目来源: [CATCTF]
题目网站: [攻防世界]

题目

题目名称

了不起的盖茨比

题目描述

小王读了盖茨比深受震撼，于是摘录本书并效仿原作者为你加密留了一段言，但他忘记给你iv了，请问你可以恢复出来原文吗
(得到的flag内容用CatCTF{}包上提交)

题目附件

from Crypto.Cipher import AES
from Crypto.Util.strxor import strxor as xor
from Crypto.Util.Padding import pad
from random import *
from base64 import *
from copy import copy
from secret import data
# data应该是CTF题目题干说的缺失的IV  iv=bytes([randint(0,2**8-1) for i in range(16)])
iva=copy(iv)
key=bytes([randint(0,2**8-1) for i in range(16)])
cipher=AES.new(key,mode=AES.MODE_ECB)
data=pad(data,16)
c=b""
for i in range(0,len(data),16):  s=data[i:i+16].ljust(16,b"\n")  c+=cipher.encrypt(xor(s,iv))  iv=xor(s,c[-16:])  key=b64encode(key)
c=b64encode(c)  print(key)
print(c)  """
b'+0zkhmid1PFjVdxSP09zSw=='
b'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'  """

WriteUp

iv是偏移量
放弃，题解如下。
crypto-了不起的盖茨比(CATCTF)_山猪儿烦不得的博客-CSDN博客

代码

# Python3
import base64
from Crypto.Cipher import AES
from Crypto.Util.strxor import strxor as xor
from Crypto.Util.number import *
import Crypto.Util.strxor as xo
import libnum, codecs, numpy as np def isChr(x):if ord('a') <= x and x <= ord('z'): return Trueif ord('A') <= x and x <= ord('Z'): return Truereturn False
def infer(index, pos):  if msg[index, pos] != 0:  return  msg[index, pos] = ord(' ')  for x in range(len(c)):if x != index:  msg[x][pos] = xo.strxor(c[x], c[index])[pos] ^ ord(' ') def know(index, pos, ch):  msg[index, pos] = ord(ch)  for x in range(len(c)):if x != index:  msg[x][pos] = xo.strxor(c[x], c[index])[pos] ^ ord(ch) def getSpace():  for index, x in enumerate(c):  res = [xo.strxor(x, y) for y in c if x!=y]  f = lambda pos: len(list(filter(isChr, [s[pos] for s in res])))  cnt = [f(pos) for pos in range(len(x))]  for pos in range(len(x)):  dat.append((f(pos), index, pos)) key = b'+0zkhmid1PFjVdxSP09zSw=='
key = base64.b64decode(key)
c=b'A0bzFxdM95YoXm64g0gZkiTloPsBAq7iV56t1M7Q4zVNxRJSTdZH0lzOMa7QyIQbKN/ftm01iZgQAk+JVgCB6hlCdMPWkdpKYHix8BTq/ClEHUPwMEjUEvgKD4tH3T/thoccBw1jfJ9RjhXbMFByWn5cyA/gHVvEEJRpII/ryKMQkzelioQ5b0MfhSy4INLqQk6yAgLzihip5ho7lDJCbYcaz85bDksOo5n9kjOfjFnjUn9G7jX+AtyhygPlGfrvauTeuPdVxqrJTVHvrzUNAqiqtCElX+BWpicP2mkZLt5B/gpquTv8U+StrdTOcr7UkWuz+YdhXkTJYUZguv7EbEnRy+M64QzqfnNf8Zk0tJQ5xOumbY8hxGTuZ8w3rWxjPKLhdgTGLgMcMYF3hPb2eqG9VZKC3T9zElI5MWPyIdkmqkrLEt6vGT8AxWJy1hl2ApkGhrJFB0DobJircN6kXUXvZXitjXSH+BA48muaRlAwK13re+zIcbI+B7+Tm3LuRT9j5NWD9RBoy+IeAQvR05IKWqEpqXEScmZsQxpAFZCSnbchYaYNAuHvBwMcMW7vTMyxROHRtyZ+gWNUhpd8CcZ9FA6w+cwQLMWW5D4nUCMK+NEsSyTBBm/jTiAp/waq+2dTVyBhbQtmm9pBtZtHJtfeVRKuZRXduNnlWDa7Wlwv0Jk2EIJpAaXxosuZnO0PHW3oX+WO5F9ydIfIJAFUpBrn4fMx3c7IJ08+bKwAfBw/johSs1ieyX/YjOOL1KbE9J6Hz3ZBBR4waQ4p9sdLsJ9UFnNghH0ZuB2F7bGoH7SurvaMglo3FyQAfM+n/EVCGWnax/JGEcw5YZuS2c7y5Gd4oOCmpFO/lVj0IaOlZsFsMgQ3GUsBT2h1yh4yarlYUczvGNyOyfUXfueCDBQJNJ7adbdra/DHpV3LXieADKED2HankT+9ACs8oVYPpZhji0UuCdvs1txytsCqPSf5l7JLDkrGP3/7Ob7UcCA4h/B+6/0xg7h+ZJ6ZR41sDpOR8S4pmPlfJkU/np52QZfplY0sKpKlaYhuhUmMSle2TAcvNUGHobNTReFV/MOfX5/HX6behFAeOwHGI14AvUbDmrmkVvbyU88DzBW2YQ/tTTiSLg/wgggkkhLd17NZAMB3XbKuw3WdkdyJfTTpyiN05DqMwV3q64fpzasFXFNQ7ix8Q/APov/TmBYtgFw4ys2jKC6Yws166RXRkrQXzY4Ey9Xvjp5i5nUgW2HLHRGz2B5lg0jI9oWjj5+89Y0Tcqb81OFD5SfeqTbg7Y2WoW6YjQ/Hzvt1l0+p/lFrnOy3ORfhwl+DFBZi4P9i+Hh7/uC1kCW8Lil2M9oVaAH4YB2yhm61AqEk4NPhSeTuioaFfvUY5lD75QiM6BdDFMTlNkC7crXmuiUpztHTzIS6E1kVARI8xsGeljjmJmuKIfQPPQfvSnnAjGeaxCNmRPDMgFGltFiGy63Pv/tVRWbUWiB27APHPsqM2qcV/nM8IwDx5xmwExl/atQXGzn/LL4xyqzmyzD+2qMeZqfzcKZWOjoWIX+SycPvc62HAQmsKqZK5ZO2JKq5OeuFEovG9oOcRYve1XStbTQYiocEbQ4XX/c6xE0cm9P/I5NM1Mlr6CT6qt3Pqb/m+7s/kwzww59FKOq5R6HmK7SHCQ6gwTQ1ciGWbJF3NLHuOpe08X4xl/l0tJengSfJRJ39Q9WwZbgBlEPf7NYeMlR9zU9QQxvZ+r4LiaJVYrQYSCcDj37Vk9XVRMijBDWDWFbK5sgkDHQYmwGYiwH4hEAqAAXDNj1/f2eRFbIU2GN6Wfj89fEINJjoG/1O/I5Q8S7tHnlWFQNoXJQ2e4r2Aca9RPLVCWz7Nq96YUKBRN3afW/9FSwWLLvjsBptQmoRj4FwmJzJf7Vj6KCOkm6mdaZ4l6FB4/E2Lk9aopD7Q473leULPM1CydXWme/8WKUqEucDwraXS57+Z+iGRMvQ8MABtZboAVFK2B1mzNL4Ba/bxVE4puy4HwvQI+N1tKmeMf99FfR13IA0y+FWL3eCzXKw8gimaJCW1e3QJJWDorDXRRjExeokMGGHzOd8MrTfNNFGWSPqZRTdGJxW7wOWQi3bHT0WSqP1fBpdU9m+WKHIxy57dL/8JFJJ97R56P76rlToRrM825JcTBEfrK0Nb9Q+2RI83vyTA2UxH9s9cSnWd+e7nacrfXjV7EjkGHgblEGHX9LqNETaZpBAL0NG9OAJ0+f+6id4/Ixcee0jx4b8k5xvblujFEdK0q2MRo2uTxSAFMpelt8JY0EZbnF9uT88N4LPms3cNeKBt0KBhx+vshFKMc/b3W7OMCo6m7EyzmcTmMe+Y6CO0x0FF0p6h1bTnJu3MMok1hO27iBSfYusHgKWVmKpgNHjiDfuBYnuBCysa+hHQZW23zxNRqi2OGAy6zCGPOY4E4nyUA6g/jlVOjq6fFv1VHN1tlQlBOCvB9r5B0os1zI2XL/Mlb9eggNuA8nw2igDm+9qkBtLxOXojAGDonAPzBagHXnVd+0kLdUGEoddt45A2fgSSociCx4tVDMd5ag1zR4VxdADAy0lnmW0n8noAT5y60SV7gICvMOphILBRjk365Mu6GNA3C+n8k5YH9sRnS7Z5EVEKdSeYigJs4XNavD50/paKnJcux2l3gzm/1aTUMzLd8tw7vZuUWv1XaYULcez8ieEMeACETyN53+RlcPQefupgszELvwlKz0prl5ydHCPOA7+ZS2zfUZOEmRSBNaIZUCd5euNg+HXMeFa/Qb452+KKEjq7vRthC4hH9gluaYMl/eXboQvvVu4xDhfVW403enI7sxdMR3t2WO1cOaLE8IN5c71W+IqhaRbJ/Prlo/pk/XAtMvimZxIN4y5/oP5vQ/lCt5jM9wAtPKSoQbJxWIYWNrXVfkZUOOwD2tlOmyxMCcKFr8921JHgtWqcYliElNX19hzmYhow+19EV3zhITzsGOX/PP1BHIKz/NJyKcGqx1hlfrDfDVedhJWkQL9sg4clbfguprs3KG5YNbbjclaK9JoEboBY3EGBGHtsWfmIRAREwy1a53y/a/NUDLaQxrMsyV/YnbiyBevGjMVNnqIY5T0YtPLL/s5Wvmq7EU9qoMDIlaosCf616TagcZalGFQumL15q6wx3FxwVB5EAjFa/MKnZNc0CqbFhXgEevp1ZXRnjEAdSK99gyAmwVawWpxIWXZQvQ5w7tIQ+nF8utoG4ab/AdLbZyKCtT8pxjiHifNcCCkLfew8Qq9S2JnrhCUMs9SEiRrLZHiE9JVlwbUJzAQjCM6G4tdeLNEApqDv4eZ7zh2U9K2+Gk9OjBgSk5xMjRkCzKCrNAKgRLoJ1Gu8L4T9LSBp1juhUsyaIaK'c = base64.b64decode(c)
cipher=AES.new(key,mode=AES.MODE_ECB)
t = []
for i in range(0,len(c),16):  if i == 0:  t.append(cipher.decrypt(c[i:i+16])) # s1 ^ iv  else: t.append(xor(cipher.decrypt(c[i:i + 16]), c[i-16:i]))
tmp = []
tmp.append(t[0])
for i in range(1, len(t)):  tttt = t[i]  for j in range(0, i):  tttt = xor(tttt, t[j])  tmp.append(tttt) # si ^ iv
# MTP attack
c = tmp
dat = []
msg = np.zeros([len(c), len(c[0])], dtype=int)
getSpace()
dat = sorted(dat)[::-1]
for w, index, pos in dat:  infer(index, pos) print(''.join([''.join([chr(c) for c in x]) for x in msg]))

结果

But a human brain is not in that class. Constantly throbbing and pulsating, it rapidly forms opinions; attaining an ability of its own; a fact which is startlingly shown by an occasional child "prodigy" in music or school work. And as, with our dumb animals, a child's inability convincingly to impart its thoughts to us, should not class it as ignorant.Upon this basis I am going to show you how a bunch of bright young folks did find a champion; a man with boys and girls of his own; a man of so dominating and happy individuality that Youth is drawn to him as is a fly to a sugar bowl. It is a story about a small town. It is not a gossipy yarn; nor is it a dry, monotonous account, full of such customary "fill-ins" as "romantic moonlight casting murky shadows down a long, winding country road." Nor will it say anything about tinklings lulling distant folds; robins carolling at twilight, nor any "warm glow of lamplight" from a cabin window. No. It is an account of up-and-doing activity; a vivid portrayal of Youth as it is today; and a practical discarding of that worn-out notion that "a child don't know anything."Now, any author, from history's dawn, always had that most important aid to writing:-an ability to call upon any word in his dictionary in building up his story. That is, our strict laws as to word construction did not block his path. But in my story that mighty obstruction will constantly stand in my path; for many an important, common word I cannot adopt, owing to its orthography."Youth! What is it? Simply a start. A start of what? Why, of that most astounding of all human functions; thought. But man didn't start his brain working. No. All that an adult can claim is a continuation, or an amplification of thoughts, dormant in his youth. Although a child's brain can absorb instruction with an ability far surpassing that of a grown man; and, although such a young brain is bound by rigid limits, it contains a capacity for constantly craving additional facts. So, in our backward Branton Hills, I just know that I can find boys and girls who can show our old moss-back Town Hall big-wigs a thing or two. Why! On Town Hall night, just go and sit in that room and find out just how stupid and stubborn a Council, (put into Town Hall, you know, through popular ballot!), can act. Say that a road is badly worn. Shall it stay so? Up jumps Old Bill Simpkins claiming that it is a townsman's duty to fix up his wagon springs if that road is too rough for him!"flag{This's_why_PCBC_is_not_living}

结果：CatCTF{This’s_why_PCBC_is_not_living}

补充资料

AES，对称加密
- python实现AES加密解密_python aes_Hello_wshuo的博客-CSDN博客

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CTF-2 了不起的盖茨比

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