104 lines
2.8 KiB
Python
104 lines
2.8 KiB
Python
import random
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from utils import AlphabetUtils as au
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from utils import CipherUtils as cu
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from chapter_three import LinearesSchieberegister as lsr
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def encrypt_text(cleartext: str, coefficients: [int], key: [int]) -> str:
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cleartext_bits = []
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for char in cleartext:
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binary_index = au.get_binary_index_of_letter(char)
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binary_index_list = []
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for bit in binary_index:
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binary_index_list.append(int(bit))
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cleartext_bits.extend(binary_index_list)
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keystream = lsr.create_shift_register(key, coefficients)
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cipher_bits = cu.xor_two_lists(cleartext_bits, keystream)
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cipher_bits_string = ''.join([str(x) for x in cipher_bits])
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return cipher_bits_string
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def decrypt_text(cipher_bits: str, coefficients: [int], key: [int]) -> str:
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cipher_bits_list = [int(cipher_bits[i:i + 1]) for i in range(0, len(cipher_bits), 1)]
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keystream = lsr.create_shift_register(key, coefficients)
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cleartext_bits = cu.xor_two_lists(cipher_bits_list, keystream)
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letter_split = [cleartext_bits[i:i + 6] for i in range(0, len(cleartext_bits), 6)]
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cleartext = ''
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for letter in letter_split:
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# Converts the list of integers to a single string
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letter_string = ''.join([str(x) for x in letter])
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cleartext += au.get_letter_at_binary_index(letter_string)
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return cleartext
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def get_optimal_shift_register_coefficients(size: int) -> [int]:
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"""
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Returns a set of coefficients for a linear shift register with the given size that guarantees a maximum bit stream.
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:param size: The size of the linear shift register
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:return: The optimal coefficients
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"""
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match size:
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case 1:
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return [1]
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case 2:
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return [1, 1]
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case 3:
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return [0, 1, 1]
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case 4:
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return [0, 0, 1, 1]
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case 5:
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return [0, 0, 1, 0, 1]
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case 6:
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return [0, 0, 0, 0, 1, 1]
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case 7:
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return [0, 0, 0, 0, 0, 1, 1]
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case 8:
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return [0, 1, 1, 0, 0, 0, 1, 1]
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case 9:
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return [0, 0, 0, 0, 1, 0, 0, 0, 1]
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case 10:
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return [0, 0, 0, 0, 0, 0, 1, 0, 0, 1]
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case 11:
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return [0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1]
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case 12:
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return [0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1]
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case 13:
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return [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1]
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case 14:
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return [0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1]
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case 15:
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return [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1]
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case _:
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return []
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def generate_random_key(size: int) -> [int]:
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"""
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Generates a random key (initial filling of a linear shift register) of the desired length
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:param size: The length of the key (must equal the length of the wanted linear shift register)
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:return: The key
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"""
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return [random.randint(0, 1) for x in range(size)]
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if __name__ == '__main__':
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size = 15
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coefficients = get_optimal_shift_register_coefficients(size)
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key = generate_random_key(size)
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print(key)
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encrypted = encrypt_text('BonkRocks', coefficients, key)
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print(encrypted)
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print(decrypt_text(encrypted, coefficients, key))
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