import socket
from Crypto.Util.number import getPrime, inverse
import re
# Fill in the right target here
HOST = 'netsec.net.in.tum.de'  # TODO
PORT = 20106  # TODO


def int_to_bytes(m):
    return m.to_bytes((m.bit_length() + 7) // 8, 'big').decode()

def modular_inverse(p, phi_q):
    x = inverse(p, phi_q)
    return x % phi_q

def decrypt_message(encrypted, p, q):
    phi_q = q - 1
    d = modular_inverse(p, phi_q)
    message = pow(encrypted, d, q)
    return message
    


def get_flag():
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    s.connect((HOST, PORT))
    sf = s.makefile('rw')  # we use a file abstraction for the sockets
    m = sf.readline().rstrip('\n')
    bit_len = int(re.search(r"[0-9]+", m).group())
    print(f"bit_len is {bit_len}")
    p = getPrime(bit_len*2)
    q = getPrime(bit_len*2)
    sf.write(f'{p};{q}\n')
    sf.flush()
    c_m = int(sf.readline().rstrip('\n'))
    print("C_M: ", c_m)
    d_m = decrypt_message(c_m, p, q)
    sf.close()
    s.close()
    print(int_to_bytes(d_m))


if __name__ == '__main__':
    get_flag()