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https://github.com/TheAlgorithms/Python.git
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132 lines
4.1 KiB
Python
132 lines
4.1 KiB
Python
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"""
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https://en.wikipedia.org/wiki/Autokey_cipher
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An autokey cipher (also known as the autoclave cipher) is a cipher that
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incorporates the message (the plaintext) into the key.
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The key is generated from the message in some automated fashion,
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sometimes by selecting certain letters from the text or, more commonly,
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by adding a short primer key to the front of the message.
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"""
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def encrypt(plaintext: str, key: str) -> str:
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"""
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Encrypt a given plaintext (string) and key (string), returning the
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encrypted ciphertext.
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>>> encrypt("hello world", "coffee")
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'jsqqs avvwo'
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>>> encrypt("coffee is good as python", "TheAlgorithms")
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'vvjfpk wj ohvp su ddylsv'
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>>> encrypt("coffee is good as python", 2)
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Traceback (most recent call last):
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...
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TypeError: key must be a string
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>>> encrypt("", "TheAlgorithms")
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Traceback (most recent call last):
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...
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ValueError: plaintext is empty
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"""
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if not isinstance(plaintext, str):
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raise TypeError("plaintext must be a string")
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if not isinstance(key, str):
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raise TypeError("key must be a string")
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if not plaintext:
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raise ValueError("plaintext is empty")
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if not key:
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raise ValueError("key is empty")
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key += plaintext
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plaintext = plaintext.lower()
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key = key.lower()
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plaintext_iterator = 0
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key_iterator = 0
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ciphertext = ""
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while plaintext_iterator < len(plaintext):
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if (
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ord(plaintext[plaintext_iterator]) < 97
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or ord(plaintext[plaintext_iterator]) > 122
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):
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ciphertext += plaintext[plaintext_iterator]
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plaintext_iterator += 1
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elif ord(key[key_iterator]) < 97 or ord(key[key_iterator]) > 122:
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key_iterator += 1
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else:
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ciphertext += chr(
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(
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(ord(plaintext[plaintext_iterator]) - 97 + ord(key[key_iterator]))
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- 97
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)
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% 26
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+ 97
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)
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key_iterator += 1
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plaintext_iterator += 1
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return ciphertext
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def decrypt(ciphertext: str, key: str) -> str:
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"""
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Decrypt a given ciphertext (string) and key (string), returning the decrypted
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ciphertext.
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>>> decrypt("jsqqs avvwo", "coffee")
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'hello world'
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>>> decrypt("vvjfpk wj ohvp su ddylsv", "TheAlgorithms")
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'coffee is good as python'
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>>> decrypt("vvjfpk wj ohvp su ddylsv", "")
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Traceback (most recent call last):
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...
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ValueError: key is empty
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>>> decrypt(527.26, "TheAlgorithms")
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Traceback (most recent call last):
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...
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TypeError: ciphertext must be a string
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"""
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if not isinstance(ciphertext, str):
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raise TypeError("ciphertext must be a string")
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if not isinstance(key, str):
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raise TypeError("key must be a string")
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if not ciphertext:
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raise ValueError("ciphertext is empty")
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if not key:
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raise ValueError("key is empty")
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key = key.lower()
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ciphertext_iterator = 0
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key_iterator = 0
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plaintext = ""
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while ciphertext_iterator < len(ciphertext):
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if (
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ord(ciphertext[ciphertext_iterator]) < 97
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or ord(ciphertext[ciphertext_iterator]) > 122
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):
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plaintext += ciphertext[ciphertext_iterator]
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else:
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plaintext += chr(
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(ord(ciphertext[ciphertext_iterator]) - ord(key[key_iterator])) % 26
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+ 97
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)
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key += chr(
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(ord(ciphertext[ciphertext_iterator]) - ord(key[key_iterator])) % 26
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+ 97
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)
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key_iterator += 1
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ciphertext_iterator += 1
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return plaintext
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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operation = int(input("Type 1 to encrypt or 2 to decrypt:"))
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if operation == 1:
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plaintext = input("Typeplaintext to be encrypted:\n")
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key = input("Type the key:\n")
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print(encrypt(plaintext, key))
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elif operation == 2:
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ciphertext = input("Type the ciphertext to be decrypted:\n")
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key = input("Type the key:\n")
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print(decrypt(ciphertext, key))
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decrypt("jsqqs avvwo", "coffee")
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