CCTF_Public/challenges/vol9_rnd1/Day1/07_Tifany/tifany.py

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2022-08-25 20:04:04 +00:00
#!/usr/bin/env python3
from Crypto.Util.number import *
from secret import PUBKEYS, flag
def keygen(nbit, k): # Public key generation function
while True:
p, q = [2 ** k * getRandomNBitInteger(nbit - k) + 1 for _ in '01']
if isPrime(p) and isPrime(q):
while True:
y = getRandomRange(2, p * q)
if pow(y, (p - 1) // 2, p) == p - 1 and pow(y, (q - 1) // 2, q) == q - 1:
pubkey = k, p * q, y
return pubkey
def encrypt(pubkey, m):
k, n, y = pubkey
assert k >= len(bin(m)[2:])
x = getRandomRange(2, n)
return pow(y, m, n) * pow(x, 2 ** k, n) % n
flag = flag.lstrip(b'CCTF{').rstrip(b'}')
flag = [bytes_to_long(flag[i*8:i*8 + 8]) for i in range(4)]
print(f'PUBKEYS = {PUBKEYS}')
ENC = [encrypt(PUBKEYS[_], flag[_]) for _ in range(4)]
print(f'ENC = {ENC}')