from Crypto.Util.number import getPrime, bytes_to_long, long_to_bytes
from math import gcd
import time

# key generation
p = getPrime(512)		# 512-bit prime number
q = getPrime(512)		# 512-bit prime number
n = p * q
phi = (p - 1) * (q - 1)
e = 65537       # = 2^16 +1 = 10000000000000001
assert gcd(e, phi) == 1

d = pow(e, -1, phi)

# encryption
def encrypt(message):
    m = bytes_to_long(message.encode())
    c = pow(m, e, n)
    return c

# decryption
def decrypt(cipher_int):
    m = pow(cipher_int, d, n)
    message = long_to_bytes(m).decode()
    return message

m = "Hello World"
c = encrypt(m)

start = time.perf_counter()
m_recover = decrypt(c)
end = time.perf_counter()

print("Ciphertext: ", c)

print("Message: ", m_recover)
print(f"decrypt time: {(end-start)*1e3:.3f} ms")