CTFshow—Crypto 13

打开题目所给文件，仅有一个base.txt，并且很长，直接跳到末尾发现等号，于是猜测应该是base32或base64。

由于base家族编码以后密文比明文更长，所以猜测base.txt是加密很多次过后的结果，由于不确定过程中究竟用了几种加密，写脚本的时候可以分情况遍历。脚本如下：

import base64

s=''
with open('base.txt', 'r', encoding='UTF-8') as f:
    s=''.join(f.readlines()).encode('utf-8')
src=s    
while True:
    try:
        src=s 
        s=base64.b16decode(s)
        str(s,'utf-8')
        continue
    except:
        pass
    try:
        src=s 
        s=base64.b32decode(s)
        str(s,'utf-8')
        continue
    except:
        pass
    try:
        src=s 
        s=base64.b64decode(s)
        str(s,'utf-8')
        continue
    except:
        pass
    break
with open('result.txt','w', encoding='utf-8') as file:
    file.write(str(src,'utf-8'))
print("Decryption complete!")

结果：