### Primary Knowledge


Decoder

import math
from Crypto.Util.number import long_to_bytes

def decrypt(c, n, e):
phi = (n - 1) // 2
d = pow(e, -1, phi)
m = pow(c, d, n)
return long_to_bytes(m)

n = 144595784022187052238125262458232959109987136704231245881870735843030914418780422519197073054193003090872912033596512666042758783502695953159051463566278382720140120749528617388336646147072604310690631290350467553484062369903150007357049541933018919332888376075574412714397536728967816658337874664379646535347
e = 65537
c = 15114190905253542247495696649766224943647565245575793033722173362381895081574269185793855569028304967185492350704248662115269163914175084627211079781200695659317523835901228170250632843476020488370822347715086086989906717932813405479321939826364601353394090531331666739056025477042690259429336665430591623215

decrypted_message = decrypt(c, n, e)
print(decrypted_message)

FLAG:

HTB{0h_d4mn_4ny7h1ng_r41s3d_t0_0_1s_1!!!}

Original writeup (https://github.com/zer00d4y/writeups/blob/main/CTF%20events/Cyber%20Apocalypse/Cyber%20Apocalypse%202024%3A%20Hacker%20Royale.md?plain=1).