Krypto_Grundlagen/utils/CipherUtils.py

from utils import AlphabetUtils as au

GERMAN_FREQUENCY_PROFILE = [
    0.0651,
    0.0189,
    0.0306,
    0.0508,
    0.1740,
    0.0166,
    0.0301,
    0.0476,
    0.0755,
    0.0027,
    0.0121,
    0.0344,
    0.0253,
    0.0978,
    0.0251,
    0.0079,
    0.0002,
    0.0700,
    0.0727,
    0.0615,
    0.0435,
    0.0067,
    0.0189,
    0.0003,
    0.0004,
    0.0113
]


def calculate_frequency(text: str, fancy_printing: bool = False):
    """
    Calculates the frequency of every letter in the german alphabet for the given text
    :param text: The text to calculate the letter frequency for
    :param fancy_printing: Whether to print the frequencies to the console
    :return: A list of frequencies, where index 0 contains the frequency of a in percent and so on.
    """
    occurrence_count = [0 for i in range(26)]

    for char in text:
        if au.is_letter_of_alphabet(char):
            char_index = au.get_index_of_letter(char)
            occurrence_count[char_index] += 1

    occurrence_frequency = []

    for count in occurrence_count:
        occurrence_frequency.append(count / len(text))

    if fancy_printing:
        for i in range(26):
            print(f'{au.get_letter_at_index(i, True)}: {occurrence_frequency[i] * 100}%')

    return occurrence_frequency


def transform_invalid_chars(input: str) -> str:
    """
    Transforms invalid characters like german umlauts into their allowed alternatives
    :param input: The text to check
    :return: The improved text
    """
    res = input
    res = res.replace('ä', 'ae')
    res = res.replace('A', 'Ae')
    res = res.replace('ö', 'oe')
    res = res.replace('Ö', 'Oe')
    res = res.replace('ü', 'ue')
    res = res.replace('Ü', 'Ue')
    res = res.replace('ß', 'ss')

    return res


def shift_char(char, incrementation: int = 1):
    """
    This method shifts one char by the value of incrementation

    :param char: Char to be shifted
    :param incrementation: How much the char should be shifted
    :return: Shifted letter
    """
    # converting character to byte
    char_in_bytes = bytes(char, 'utf-8')[0]
    if char_in_bytes + incrementation >= 91 and char_in_bytes < 91 \
            or char_in_bytes + incrementation >= 123:  # z -> 122 | 90 -> Z so go backwards
        new_char_in_bytes = bytes([char_in_bytes - (26 - incrementation)])
    else:
        new_char_in_bytes = bytes([char_in_bytes + incrementation])

    return str(new_char_in_bytes)[2]


def xor_two_lists(clear_list: [int], key_list: [int]) -> [int]:
    """
    XORs every element of the first given list with the corresponding element of the 2nd list.
    If the 2nd list is shorter than the first one, the XORing starts at the first element of the
    2nd list again once all elements have been used and so on.
    :param clear_list: The first list
    :param key_list: The second list. This list may be shorter or longer than the first one, doesn't matter
    :return: A list containing the XORed elements.
    """
    xored_list = []

    for x in range(len(clear_list)):
        xored_list.append(clear_list[x] ^ key_list[x % len(key_list)])

    return xored_list


if __name__ == '__main__':
    print(
        calculate_frequency('Hier den Text eingeben, für den die Wahrscheinlichkeiten berechnet werden sollen', True))