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def chaocipher_encrypt(message: str) -> str:
"""
Encrypts a message using the Chaocipher algorithm.
Chaocipher is a symmetric encryption algorithm that uses two mixed alphabets to
perform a double substitution on each letter of the plaintext. The two alphabets
are predetermined and fixed.
Args:
message: The message to be encrypted.
Returns:
The encrypted message.
"""
# Define the Chaocipher alphabets
left_alphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"
right_alphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC"
ciphertext = ""
left_index = 0
right_index = 0
# Loop through each character in the message
for char in message.upper():
if not char.isalpha():
# Ignore non-alphabetic characters
ciphertext += char
continue
# Find the index of the character in the left alphabet
left_char_index = left_alphabet.index(char)
# Swap the left and right indices
left_index, right_index = right_index, left_index
# Find the corresponding character in the right alphabet
right_char_index = (left_char_index + right_index) % 26
right_char = right_alphabet[right_char_index]
# Append the encrypted character to the ciphertext
ciphertext += right_char
return ciphertext
def chaocipher_decrypt(ciphertext: str) -> str:
"""
Decrypts a message that has been encrypted using the Chaocipher algorithm.
Args:
ciphertext: The message to be decrypted.
Returns:
The decrypted message.
"""
# Define the Chaocipher alphabets
left_alphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"
right_alphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC"
plaintext = ""
left_index = 0
right_index = 0
# Loop through each character in the ciphertext
for char in ciphertext.upper():
if not char.isalpha():
# Ignore non-alphabetic characters
plaintext += char
continue
# Find the index of the character in the right alphabet
right_char_index = right_alphabet.index(char)
# Swap the left and right indices
left_index, right_index = right_index, left_index
# Find the corresponding character in the left alphabet
left_char_index = (right_char_index - right_index) % 26
left_char = left_alphabet[left_char_index]
# Append the decrypted character to the plaintext
plaintext += left_char
return plaintext
# Example usage
message = "Hello World!"
ciphertext = chaocipher_encrypt(message)
print(f"Ciphertext: {ciphertext}")
plaintext = chaocipher_decrypt(ciphertext)
print(f"Plaintext: {plaintext}")
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