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114 lines
4.4 KiB
114 lines
4.4 KiB
# APPROACH: All keyboard keys can be interpreted as an ASCII-Code.
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# => Shift them on the ascii table, with the factor of shift
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# COMMENT: Admittedly, this cipher everything else then secure, but it serves its purpose.
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# => This implementation can create 256 different encryption mappings
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import time
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def shift_cipher(shift):
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codes = {}
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for char_code in range(0, 255): # all ASCII-letters
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char = chr((char_code + shift) % 255)
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codes[chr(char_code)] = char
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return codes
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# OBSERVATION: If the encryption map is known, anyone can decode the text.
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# => Security of this procedure depends on how many combinations the cipher algorithm creates.
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# COMMENT: Thanks to the weak cipher, a brute force attack cracks the encryption after a maximum of 256 attempts.
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def caesar(text, cipher, mode):
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mode = mode.upper()
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if mode not in ["ENCODE", "DECODE"]: # Use 'in' to check for multiple conditions
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return text
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tokens = list(text)
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if mode == "DECODE":
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cipher = {value: key for key, value in cipher.items()}
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for i in range(len(tokens)):
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if tokens[i] in cipher: # Check if the character exists in the cipher before replacing
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tokens[i] = cipher[tokens[i]]
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return "".join(tokens)
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# COMMENT: Ciphers are binary bijective mappings over an alphabet A, of which |A|! exist (for ours 256!).
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# In practice, security should be strengthened through better cipher algorithms.
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# Because our cipher works so poorly, here is an optimized variant of the caesar process.
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# APPROACH: Set a starting position for the encryption and then encrypt recursively to the right and left.
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# => An Encryption can only be successful, if the starting point is known.
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# => An brute force attack cracks the encryption after a maximum of 256*len(text) attempts.
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def caesar_amplified(text, pos, cipher, mode):
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mode = mode.upper()
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if mode not in ["ENCODE", "DECODE"]: # Use 'in' to check for multiple conditions
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return text
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tokens = list(text)
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if mode == "DECODE":
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cipher = {value: key for key, value in cipher.items()}
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tokens[pos] = cipher[tokens[pos]]
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tokens = caesar_recursive(tokens, pos - 1, cipher, "l") # start left recursion
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tokens = caesar_recursive(tokens, pos + 1, cipher, "r") # start right recursion
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return "".join(tokens)
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def caesar_recursive(tokens, pos, cipher, mode):
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if pos == -1 or pos == len(tokens):
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return tokens
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cipher = update_cipher(cipher)
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tokens[pos] = cipher[tokens[pos]]
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if mode == "l":
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return caesar_recursive(tokens, pos - 1, cipher, "l")
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else:
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return caesar_recursive(tokens, pos + 1, cipher, "r")
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def update_cipher(codes_old):
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codes_new = {}
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for key, value in codes_old.items():
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codes_new[key] = codes_old[codes_old[key]]
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return codes_new
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# Write message into these lines:
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string = '''
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Liebe/r Empfänger,
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Herzliche Grüße aus dem hohen Norden! Ich hoffe, diese Nachricht erreicht dich in guter Verfassung und fügt einen Hauch
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von festlicher Stimmung zu deinem Tag hinzu.
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Santa und seine Wichtel arbeiten fleißig daran, diese Jahreszeit für alle magisch zu gestalten. Die Werkstatt ist voller
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Aktivität, während Spielzeuge mit Sorgfalt hergestellt werden.
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Ich wünsche dir Freude, Gelächter und einen festlichen Geist, der dein Herz erwärmt. Genieße die Magie der Feiertage!
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Herzliche Grüße,
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Rudolph
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'''
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enc_time = time.time()
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encoded = caesar(string, shift_cipher(2), "ENCODE")
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enc_time = (time.time() - enc_time) * 1000 # Convert to milliseconds
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dec_time = time.time()
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decoded = caesar(encoded, shift_cipher(2), "DECODE")
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dec_time = (time.time() - dec_time) * 1000 # Convert to milliseconds
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print("Encoded Caesar-Encryption: (calculated in " + str(enc_time) + "ms)")
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print(encoded + "\n")
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print("Decoded Caesar-Encryption: (calculated in " + str(dec_time) + "ms)")
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print(decoded)
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print("\n")
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enc_rec_time = time.time()
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encoded_rec = caesar_amplified(string, 5, shift_cipher(2), "ENCODE")
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enc_rec_time = (time.time() - enc_rec_time) * 1000 # Convert to milliseconds
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dec_rec_time = time.time()
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decoded_rec = caesar_amplified(encoded_rec, 5, shift_cipher(2), "DECODE")
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dec_rec_time = (time.time() - dec_rec_time) * 1000 # Convert to milliseconds
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print("Encoded Caesar-Encryption amplified: (calculated in " + str(enc_rec_time) + "ms)")
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print(encoded_rec + "\n")
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print("Decoded Caesar-Encryption amplified: (calculated in " + str(dec_rec_time) + "ms)")
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print(decoded_rec)
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