Krypto_Grundlagen/chapter_one/Verschiebe-Chiffre.py

from utils import CipherUtils


def encrypt_text(cleartext: str = 'Bitcoin', incrementation: int = 13):
    """
    This method encrypts a text by shifting each letter by the value of incrementation

    :param cleartext: The secret message to encrypt
    :param incrementation: How much the letters should be shifted
    :return: Encrypted text
    """
    return shift_text(cleartext, (incrementation % 26))  # '%' to repeat after 26 with 0


def decrypt_text(encrypted_text: str = 'Ovgpbva', incrementation: int = 13):
    """
    This method decrypts a text by shifting each letter by the value of incrementation

    :param encrypted_text: The encrypted secret message to decrypt
    :param incrementation: How much the letters should be shifted
    :return: Decrypted text
    """
    return shift_text(encrypted_text, 26 - (incrementation % 26))  # '%' to repeat after 26 with 0


def shift_text(cleartext: str, incrementation: int):
    """
    This method shifts every letter of a string by the value of incrementation
    :param cleartext: The string to be shifted
    :param incrementation: How much the letters should be shifted
    :return: Shifted text
    """
    shifted_text = ''

    for char in cleartext:
        shifted_text += CipherUtils.shift_char(char, incrementation)

    return shifted_text


def brute_force_example(cleartext: str = 'Bitcoin', incrementation: int = 7):
    """
    This is an example of how to bruteforce an encrypted text. (Encrypted with Letter-Shifting)

    :param cleartext: The secret message to encrypt and decrypt during bruteforcing
    :param incrementation: How much the letters should be shifted
    """
    encrypted_text = encrypt_text(cleartext, incrementation=incrementation)

    for x in range(26):
        if cleartext == decrypt_text(encrypted_text, incrementation=x):
            print(f'Text was shifted by {x} letters.')


if __name__ == '__main__':
    print(encrypt_text())
    print(decrypt_text())

    brute_force_example()