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#!/usr/bin/env python3
from Crypto.PublicKey import RSA
from Crypto.Util.number import long_to_bytes
from math import isqrt, inf
from tqdm import tqdm
pubkey = RSA.importKey(open("pubkey.pem").read())
# Small primes can be found with naive approach.
for i in tqdm(range(3, isqrt(pubkey.n), 2), total=inf):
if pubkey.n % i == 0:
p = i
break
else:
raise
q = pubkey.n // p
phi = (p-1)*(q-1)
d = pow(pubkey.e, -1, phi)
ciphertext = int(open("message.txt").read())
plaintext = pow(ciphertext, d, pubkey.n)
print(long_to_bytes(plaintext).decode())
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