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]


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