b2123_[0xGame-2022] [MISC]_babyRe writeup

题目：

先是pyc反编译，用在线工具或者uncompyle6都可以，得到原来的加密代码

# uncompyle6 version 3.8.0# Python bytecode 2.7 (62211)# Decompiled from: Python 3.9.13 (main, Jun  8 2022, 09:45:57) # [GCC 11.3.0]# Embedded file name: 1.py# Compiled at: 2022-08-22 17:01:47import base64def encode(str):    fflag = '0'    for i in range(1, len(flag)):        x = ord(flag[i]) ^ ord(flag[(i - 1)])        x += 30        fflag += chr(x)    return base64.b64encode(fflag)flag = open('flag.txt').read()enc = encode(flag)print enc# okay decompiling flag.pyc

加密函数就是将原flag的每一位与上一位异或的结果再加30最后整体base64加密

import base64cipher=open(r"C:Users16334Desktopout.txt").read()ccipher=base64.b64decode(cipher)flag='0'for i in range(1,len(ccipher)):    a=ccipher[i]-30    flag+=chr(ord(flag[i-1])^a)print(flag)