BUUCTF 每日打卡 2021-7-28

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我是靠谱客的博主默默小霸王，最近开发中收集的这篇文章主要介绍BUUCTF 每日打卡 2021-7-28，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

引言

无

[De1CTF2019]xorz

加密代码如下：

from itertools import *
from data import flag,plain

key=flag.strip("de1ctf{").strip("}")
assert(len(key)<38)
salt="WeAreDe1taTeam"
ki=cycle(key)
si=cycle(salt)
cipher = ''.join([hex(ord(p) ^ ord(next(ki)) ^ ord(next(si)))[2:].zfill(2) for p in plain])
print cipher
# output:
# 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

有plain，有key，不禁让人想起维吉尼亚密码，想起之前做过的一道[NCTF2019]Sore
于是就参照维吉尼亚的爆破方法来解题，参考示例代码
首先是Kasiski 实验：

def GCD(step):
    gcd_list = []
    buf = []
    if not len(step):
        return "None has ben found"
    else:  # find GCD
        step_min = max(step) // 2
        for con in range(2, step_min + 1):
            flag = True
            for each_step in step:
                if each_step % con:
                    flag = False
                    break
            if flag:
                gcd_list.append(con)
    if len(gcd_list):
        return gcd_list
    else:  # find GCD list
        for con in range(2, step_min + 1):
            gcd_list.append([con, len(step)])
            for each_step in step:
                if each_step % con:
                    gcd_list[con - 2][1] -= 1
        for each in gcd_list:
            if each[1]:
                buf.append(each)
        for i in range(1, len(buf)):
            j = i
            while j > 0:
                if buf[j][1] < buf[j - 1][1]:
                    tem = buf[j - 1]
                    buf[j - 1] = buf[j]
                    buf[j] = tem
                j -= 1
        return buf

def find(string1, string2):
    k, t = 0, 0
    for t in range(len(string1)):
        if string1[t] == string2[0] and t+len(string2) <= len(string1):
            for k in range(len(string2)):
                if string1[t+k] != string2[k]:
                    k -= 1
                    break
            if k == len(string2)-1:
                break
    if t == len(string1)-1 or string1 == '':
        return -1
    else:
        return t

def kasiski(cipher):
    sec_msg = cipher
    step = []
    flag = False
    lenth = len(sec_msg)
    for i in range(lenth - 5):
        flag_tem = 0
        i_tem = i
        while True:
            print(sec_msg[i_tem + 3:], sec_msg[i_tem:i_tem + 3])
            flag_tem = find(sec_msg[i_tem + 3:], sec_msg[i_tem:i_tem + 3])
            # flag_tem = sec_msg[i_tem + 3:].find(sec_msg[i_tem:i_tem + 3])
            print(flag_tem)
            if flag_tem == -1:
                break
            flag_tem += 3
            step.append(flag_tem)
            i_tem += flag_tem
    # print('step:', step)
    print(GCD(step))
    return GCD(step)

if __name__ == '__main__':
    cipher = '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'
    kasiski(cipher)

稍微修改了一下原代码，放弃了原来只对字符串起作用的.find()方法，重新定义了一个find函数，使得对列表也管用
这里选用的cipher是[NCTF2019]Sore中的cipher，试验与结果相吻合
在这里插入图片描述
得到本题的key的长度代码如下：

from itertools import *
from kasiski import *

salt = "WeAreDe1taTeam"
si = cycle(salt)
c = '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'
list_c = []
for i in range(0, len(c), 2):
    list_c.append(int(c[i:i + 2], 16) ^ ord(next(si)))
print(list_c)
len_key = max(kasiski(list_c))
print(len_key)

结果为：
在这里插入图片描述
后来找wp时发现也是正确的
但是下一步重合指数攻击和字母频率分析出现了瓶颈，原来的维吉尼亚密码爆破采用的把加密视作凯撒密码，只要进行位移即可，但本题是异或加密，几乎是重新把脚本写一遍了
直接找到了官方wp，稍微修改了一下：

from itertools import cycle

c = "49380d773440222d1b421b3060380c3f403c3844791b202651306721135b6229294a3c3222357e766b2f15561b35305e3c3b670e49382c295c6c170553577d3a2b791470406318315d753f03637f2b614a4f2e1c4f21027e227a4122757b446037786a7b0e37635024246d60136f7802543e4d36265c3e035a725c6322700d626b345d1d6464283a016f35714d434124281b607d315f66212d671428026a4f4f79657e34153f3467097e4e135f187a21767f02125b375563517a3742597b6c394e78742c4a725069606576777c314429264f6e330d7530453f22537f5e3034560d22146831456b1b72725f30676d0d5c71617d48753e26667e2f7a334c731c22630a242c7140457a42324629064441036c7e646208630e745531436b7c51743a36674c4f352a5575407b767a5c747176016c0676386e403a2b42356a727a04662b4446375f36265f3f124b724c6e346544706277641025063420016629225b43432428036f29341a2338627c47650b264c477c653a67043e6766152a485c7f33617264780656537e5468143f305f4537722352303c3d4379043d69797e6f3922527b24536e310d653d4c33696c635474637d0326516f745e610d773340306621105a7361654e3e392970687c2e335f3015677d4b3a724a4659767c2f5b7c16055a126820306c14315d6b59224a27311f747f336f4d5974321a22507b22705a226c6d446a37375761423a2b5c29247163046d7e47032244377508300751727126326f117f7a38670c2b23203d4f27046a5c5e1532601126292f577776606f0c6d0126474b2a73737a41316362146e581d7c1228717664091c"


def getCipher(c):
    codeintlist = []
    codeintlist.extend(
        (map(lambda i: int(c[i:i + 2], 16), range(0, len(c), 2))))
    salt = "WeAreDe1taTeam"
    si = cycle(salt)
    newcodeintlist = [ci ^ ord(next(si)) for ci in codeintlist]
    return newcodeintlist


def getKeyPool(cipher, stepSet, plainSet, keySet):
    ''' 传入的密文串、明文字符集、密钥字符集、密钥长度范围均作为数字列表处理.形如[0x11,0x22,0x33]
        返回一个字典，以可能的密钥长度为键，以对应的每一字节的密钥字符集构成的列表为值，密钥字符集为数字列表。
            形如{
                    1:[[0x11]],
                    3:[
                        [0x11,0x33,0x46],
                        [0x22,0x58],
                        [0x33]
                       ]
                }
    '''
    keyPool = dict()
    for step in stepSet:
        maybe = [None] * step
        for pos in range(step):
            maybe[pos] = []
            for k in keySet:
                flag = 1
                for c in cipher[pos::step]:
                    if c ^ k not in plainSet:
                        flag = 0
                if flag:
                    maybe[pos].append(k)
        for posPool in maybe:
            if len(posPool) == 0:
                maybe = []
                break
        if len(maybe) != 0:
            keyPool[step] = maybe
    return keyPool


def calCorrelation(cpool):
    '''传入字典，形如{'e':2,'p':3}
        返回可能性，0~1,值越大可能性越大
        (correlation between the decrypted column letter frequencies and
        the relative letter frequencies for normal English text)
    '''
    frequencies = {"e": 0.12702, "t": 0.09056, "a": 0.08167, "o": 0.07507, "i": 0.06966,
                   "n": 0.06749, "s": 0.06327, "h": 0.06094, "r": 0.05987, "d": 0.04253,
                   "l": 0.04025, "c": 0.02782, "u": 0.02758, "m": 0.02406, "w": 0.02360,
                   "f": 0.02228, "g": 0.02015, "y": 0.01974, "p": 0.01929, "b": 0.01492,
                   "v": 0.00978, "k": 0.00772, "j": 0.00153, "x": 0.00150, "q": 0.00095,
                   "z": 0.00074}
    relative = 0.0
    total = 0
    fpool = 'etaoinshrdlcumwfgypbvkjxqz'
    total = sum(cpool.values())  # 总和应包括字母和其他可见字符
    for i in cpool.keys():
        if i in fpool:
            relative += frequencies[i] * cpool[i] / total
    return relative


def analyseFrequency(cfreq):
    key = []
    for posFreq in cfreq:
        mostRelative = 0
        for keyChr in posFreq.keys():
            r = calCorrelation(posFreq[keyChr])
            if r > mostRelative:
                mostRelative = r
                keychar = keyChr
        key.append(keychar)
    return key


def getFrequency(cipher, keyPoolList):
    ''' 传入的密文作为数字列表处理
        传入密钥的字符集应为列表，依次包含各字节字符集。
            形如[[0x11,0x12],[0x22]]
        返回字频列表，依次为各字节字符集中每一字符作为密钥组成部分时对应的明文字频
            形如[{
                    0x11:{'a':2,'b':3},
                    0x12:{'e':6}
                 },
                 {
                    0x22:{'g':1}
                 }]
    '''
    freqList = []
    keyLen = len(keyPoolList)
    for i in range(keyLen):
        posFreq = dict()
        for k in keyPoolList[i]:
            posFreq[k] = dict()
            for c in cipher[i::keyLen]:
                p = chr(k ^ c)
                posFreq[k][p] = posFreq[k][p] + 1 if p in posFreq[k] else 1
        freqList.append(posFreq)
    return freqList


def vigenereDecrypt(cipher, key):
    plain = ''
    cur = 0
    ll = len(key)
    for c in cipher:
        plain += chr(c ^ key[cur])
        cur = (cur + 1) % ll
    return plain


def main():
    ps = []
    ks = []
    ss = []
    ps.extend(range(32, 127))
    ks.extend(range(0xff + 1))
    ss.extend(range(38))
    cipher = getCipher(c)

    keyPool = getKeyPool(cipher=cipher, stepSet=ss, plainSet=ps, keySet=ks)
    for i in keyPool:
        freq = getFrequency(cipher, keyPool[i])
        key = analyseFrequency(freq)
        plain = vigenereDecrypt(cipher, key)
        print(plain, "n")
        print(''.join(map(chr, key)))


if __name__ == '__main__':
    main()

思想与维吉尼亚密码爆破相同，利用plain是一段有意义的字符，统计字母频率来得到key和plain
结果如下：
在这里插入图片描述
容易发现，得到的key的第二位是不对的
经过修改，结果为：W3lc0m3tOjo1nu55un1ojOt3q0cl3W

出了官方给出的解法，还找到了另一种解法，使得密文不同位置对应的同一key的字母之间的汉明距离最小来得到key的长度，进而还原key和plain
至于什么是汉明距离，摘自百度百科：
在这里插入图片描述
代码如下：

import string
from binascii import unhexlify, hexlify
from itertools import *


def bxor(a, b):  # xor two byte strings of different lengths
    if len(a) > len(b):
        return bytes([x ^ y for x, y in zip(a[:len(b)], b)])
    else:
        return bytes([x ^ y for x, y in zip(a, b[:len(a)])])


def hamming_distance(b1, b2):
    differing_bits = 0
    for byte in bxor(b1, b2):
        differing_bits += bin(byte).count("1")
    return differing_bits


def break_single_key_xor(text):
    key = 0
    possible_space = 0
    max_possible = 0
    letters = string.ascii_letters.encode('ascii')
    for a in range(0, len(text)):
        maxpossible = 0
        for b in range(0, len(text)):
            if (a == b):
                continue
            c = text[a] ^ text[b]
            if c not in letters and c != 0:
                continue
            maxpossible += 1
        if maxpossible > max_possible:
            max_possible = maxpossible
            possible_space = a
    key = text[possible_space] ^ 0x20
    return chr(key)


salt = "WeAreDe1taTeam"
si = cycle(salt)
b = unhexlify(
    b'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')
plain = ''.join([hex(ord(c) ^ ord(next(si)))[2:].zfill(2) for c in b.decode()])
b = unhexlify(plain)
print(plain)

normalized_distances = []

for KEYSIZE in range(2, 40):
    n = len(b) // KEYSIZE
    list_b = []
    for i in range(n - 1):
        list_b.append(b[i * KEYSIZE: (i + 1) * KEYSIZE])

    normalized_distance = 0
    for i in range(len(list_b) - 1):
        normalized_distance += hamming_distance(list_b[i], list_b[i + 1])
    normalized_distance = float(normalized_distance) / (KEYSIZE * (len(list_b) - 1))

    normalized_distances.append(
        (KEYSIZE, normalized_distance)
    )
normalized_distances = sorted(normalized_distances, key=lambda x: x[1])
print(normalized_distances)

for KEYSIZE, _ in normalized_distances[:5]:
    block_bytes = [[] for _ in range(KEYSIZE)]
    for i, byte in enumerate(b):
        block_bytes[i % KEYSIZE].append(byte)
    keys = ''
    try:
        for bbytes in block_bytes:
            keys += break_single_key_xor(bbytes)
        key = bytearray(keys * len(b), "utf-8")
        plaintext = bxor(b, key)
        print("keysize:", KEYSIZE)
        print("key is:", keys)
        s = bytes.decode(plaintext)
        print(s)
    except Exception:
        continue

对代码进行了一些修改，得到结果：
在这里插入图片描述
经过测试，在某些情况下，该程序对key长度的计算会有偏差，会出现key内容缺失，或者重复的情况，但是对plain的还原比较准确
与第一种方法相比各有优劣
以key = 'a24jq354qgikamzasmglzhjapwmiq3OMM93FI'为例
方法一的结果为：
在这里插入图片描述
方法二的结果为：

具体解题时，可以对照着看