BUUCTF [GUET-CTF2019]虚假的压缩包 1

import gmpy2
"""
gmpy2.mpz(n)#初始化一个大整数
gmpy2.mpfr(x)# 初始化一个高精度浮点数x
d = gmpy2.invert(e,n) # 求逆元，de = 1 mod n
C = gmpy2.powmod(M,e,n)# 幂取模，结果是 C = (M^e) mod n
gmpy2.is_prime(n) #素性检测
gmpy2.gcd(a,b)  #欧几里得算法，最大公约数
gmpy2.gcdext(a,b)  #扩展欧几里得算法
gmpy2.iroot(x,n) #x开n次根
"""
p = gmpy2.mpz(3)
q = gmpy2.mpz(11)
e = gmpy2.mpz(3)
l = (p-1) * (q-1)
d = gmpy2.invert(e,l)
c = gmpy2.mpz(26)
n = p * q
ans = pow(c,d,n)
print(ans)

来源:https://blog.csdn.net/qq_24033605/article/details/117158714

import os
import binascii
import struct

crcbp = open("1.png", "rb").read()    #打开图片!!!
for i in range(2000):
    for j in range(2000):
        data = crcbp[12:16] + \
            struct.pack('>i', i)+struct.pack('>i', j)+crcbp[24:29]
        crc32 = binascii.crc32(data) & 0xffffffff
        if(crc32 == 0x1670BAE6):    #修改为图片当前CRC!!!
            print(i, j)
            print('hex:', hex(i), hex(j))

import binascii

# 打开文件进行读取
with open('file', 'r') as f1:
    data = f1.read()

# 初始化变量存储解密后的数据
flag_data = ""

# 对每个字符进行异或操作
for i in data:
    tmp = int(i, 16) ^ 5
    flag_data += hex(tmp)[2:]

# 将解密后的数据写入新文件
with open('./flag.doc', 'wb') as f2:
    # 使用 binascii.unhexlify 替代 decode('hex')
    f2.write(binascii.unhexlify(flag_data))

print("Decryption complete.")

FLAG{_th2_7ru8_2iP_}   
flag{_th2_7ru8_2iP_}