TEST.py

import random
import math

def is_prime(number):
    if number <= 1:
        return False
    elif number <= 3:
        return True
    elif number % 2 == 0 or number % 3 == 0:
        return False
    i = 5
    while i * i <= number:
        if number % i == 0 or number % (i + 2) == 0:
            return False
        i += 6
    return True

def gcd(a, b):
    while b != 0:
        a, b = b, a % b
    return a

def mod_inverse(a, m):
    m0, x0, x1 = m, 0, 1
    while a > 1:
        q = a // m
        m, a = a % m, m
        x0, x1 = x1 - q * x0, x0
    return x1 + m0 if x1 < 0 else x1

def generate_keypair(p, q):
    if not (is_prime(p) and is_prime(q)):
        raise ValueError("Both numbers must be prime.")
    elif p == q:
        raise ValueError("p and q cannot be equal.")

    n = p * q
    phi = (p - 1) * (q - 1)

    e = random.randrange(1, phi)
    g = gcd(e, phi)
    while g != 1:
        e = random.randrange(1, phi)
        g = gcd(e, phi)

    d = mod_inverse(e, phi)
    return ((e, n), (d, n))

def encrypt(public_key, plaintext):
    e, n = public_key
    cipher = [pow(ord(char), e, n) for char in plaintext]
    return cipher

def decrypt(private_key, ciphertext):
    d, n = private_key
    plain = [chr(pow(char, d, n)) for char in ciphertext]
    return ''.join(plain)

if __name__ == "__main__":
    # Example usage
    p = 7
    q = 19
    public_key, private_key = generate_keypair(p, q)
    print("Public Key:", public_key)
    print("Private Key:", private_key)

    message = "Hello, RSA!"
    print("Original Message:", message)

    encrypted_message = encrypt(public_key, message)
    print("Encrypted Message:", encrypted_message)

    decrypted_message = decrypt(private_key, encrypted_message)
    print("Decrypted Message:", decrypted_message)