one_time_pad.py

"""
Implementation of the famous one time pad / Vernam Cipher

In practice we need a way to generate random keys which I havn't included.

Programmed by Aladdin Persson <aladdin.persson at hotmail dot com>
*  2019-11-12 Initial programming

"""


def xor(s1, s2):
    xor_result = []

    for i in range(min(len(s1), len(s2))):
        xor_result.append(int(s1[i]) ^ int(s2[i]))  # xor

    return xor_result


def encrypt(message, key):
    binary_message = ""
    binary_key = ""
    ciphered_text = ""

    for letter in message:
        binary_message += format(ord(letter), "b")

    for letter in key:
        binary_key += format(ord(letter), "b")

    cipher_binary = xor(binary_message, binary_key)

    return "".join(str(e) for e in cipher_binary)


def decrypt(cipher_text, key):
    binary_key = ""
    decrypted_text = ""

    for letter in key:
        binary_key += format(ord(letter), "b")

    binary_message = xor(cipher_text, binary_key)

    for i in range(0, len(binary_message), 7):
        letter = "".join(str(e) for e in binary_message[i : i + 7])
        decrypted_text += chr(int(letter, 2))

    return decrypted_text


def main():
    message = "cheesecake"  # 'secret' message
    key = "randomrandomrandom"  #'random' key

    encrypted = encrypt(message, key)
    decrypted = decrypt(encrypted, key)

    print("Original message: " + str(message))
    print("Encrypted message (in binary): " + str(encrypted))
    print("Decrypted message: " + str(decrypted))


if __name__ == "__main__":
    main()