def cipher_decrypt(ciphertext, key):
assert key < 2**16, '16-bit key please'
assert key >= 0, '16-bit key please'
prg = MT19937(key)
key_stream = generate_bytes(prg, len(ciphertext))
return xor(ciphertext, key_stream)
def analyze_password_reset_token(token):
current_time = int(time.time())
for possible_seed in range(current_time - 100, current_time + 50):
prg = MT19937(possible_seed)
if prg.extract_number() == token:
return True
return False
def crack_seed(random_number):
current_time = int(time.time())
for possible_seed in range(current_time - 100, current_time + 40):
prg = MT19937(possible_seed)
if prg.extract_number() == random_number:
return possible_seed
assert False, 'did not cracked the seed'
def generate_random():
a = 2
b = 10
time.sleep(random.randint(a, b))
seed = int(time.time())
prg = MT19937(seed)
time.sleep(random.randint(a, b))
return seed, prg.extract_number()
def main():
prg, random_numbers = generate_randoms()
untempered_numbers = np.array([untemper(i) for i in random_numbers])
cloned_prg = MT19937(123)
cloned_prg.mt = untempered_numbers
new_numbers = [(prg.extract_number(), cloned_prg.extract_number())
for _ in range(1000)]
for i, j in new_numbers:
assert i == j
print("challenge 3.23 completed.")
def generate_password_reset_token():
seed = int(time.time())
prg = MT19937(seed)
return prg.extract_number()
def generate_randoms():
seed = 666
prg = MT19937(seed)
return prg, [prg.extract_number() for _ in range(624)]