17.NSCTF web200

This problem is not easy, direct programming can

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I'm just pasting my Python code in.

#!/usr/bin/python
#coding=utf-8

Import base64

#ror13Encryption function (ciphertext incoming is decryption, plaintext incoming is encryption)
Def rot13(s, OffSet=13):
    Def encodeCh(ch):
        f=lambda x: chr((ord(ch)-x+OffSet) % 26 + x)
        Return f(97) if ch.islower() else (f(65) if ch.isupper() else ch)
    Return ‘‘.join(encodeCh(c) for c in s)

Def decode(strs):
    Flag = ""#Save flag
    Flag_x = ""#Get every character in the flag
    
    Strs = strs[::-1]#reverse string
    
    Strs = base64.b64decode(strs)#base64 decoding
    
    For i in strs:# traverse every character
        
        Flag_x = ord(i)-1#Each character ascii code-1
        Flag_x = chr(flag_x)#convert bit string
        Flag = flag+flag_x#string connection
        
    Flag = flag[::-1]#reverse the string
    Return flag# get flag

Def main():
    Strs = "a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws"# password to be cracked
    Flag = rot13(strs)#rot13decrypt
    Flag = decode(flag)#title decryption
    Print flag#output flag

If __name__ == "__main__":
    Main()  

Note: Where ROT13 is the code to find online

The results are as follows:

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17.NSCTF web200