ctf-writeup/2023/KnightCTF 2023/I Love Pi/README.md

I Love Pi

Isaac Newton left me this piece of code and a message. Can you help me decode this...

About the Challenge

We were given a python script and an encoded text, The python script will be look like this (You can get the script here)

import base64

lengths = [--REDACTED--] 
flag = "KCTF{*******************************}"

# len(lengths) = 10
# len(flag) = 39

s = 0
encoded_flag = ""
for l in lengths:
    seg = flag[s:s+l]
    for _ in range(len(seg)):
        seg = base64.b64encode(seg.encode('ascii')).decode('ascii')
    s+=l
    encoded_flag += seg
    
print(encoded_flag)

And here is the encoded flag

VXpCT1ZRPT0=Rg==V2xod1UxcHNWa0pRVkRBOQ==MQ==VmpCb2QxVXhjSE5UYTFaV1ZrUkJPUT09Vm0wd2QyVkhVWGhUV0doaFUwVndVRlp0TVZOV01XeFZVbTVrVlUxV2NIbFdNalZyVmpKS1NHVkliRmRpVkVaSVZtMTRTMk15VGtWUmJIQk9VakF4TkZkWGRHRmtNRFZ5VFZWV2FHVnFRVGs9U0RNPQ==Vm1wQ1UxRXlTbkpOVldSVFYwZFNjVlJVU1RSUFVUMDk=VjFSS2QxWXhjSEpPVldSYVpXcEJPUT09VGtac09RPT0=

The python script will encode each part of the flag with base64

How to Solve?

To solve this, Im only using cyberchef to decode the encoded text and notepad to merge the string that i have found without creating any python script haha. Anyway here is the flag

KCTF{4_P1_4_D4Y_K33P5_7H3_H4CK3r5_4W4Y}