bugkuctf 密码学_简单加密writeup

密文：e6Z9i~]8R~U~QHE{RnY{QXg~QnQ{^XVlRXlp^XI5Q6Q6SKY8jUAA

因为末尾是AA与base64结尾的==相似，推断为base64和凯撒加密的结合。

=的ascii码为61，A为65.即前移四位。

首先将其转换为ASCII码（在线工具）为：101,54,90,57,105,126,93,56,82,126,85,126,81,72,69,123,82,110,89,123,81,88,103,126,81,110,81,123,94,88,86,108,82,88,108,112,94,88,73,53,81,54,81,54,83,75,89,56,106,85,65,65

再写个Python脚本解密

import base64
m=[101,54,90,57,105,126,93,56,82,126,85,126,81,72,69,123,82,110,89,123,81,88,103,126,81,110,81,123,94,88,86,108,82,88,108,112,94,88,73,53,81,54,81,54,83,75,89,56,106,85,65,65]
flag=''
i=4
for j in m:
    flag+=chr(j-i)
flag=base64.b64decode(flag).decode()
print(flag)