Add autoclave cipher

ciphers/autokey.py

@@ -0,0 +1,131 @@
+"""
+https://en.wikipedia.org/wiki/Autokey_cipher
+An autokey cipher (also known as the autoclave cipher) is a cipher that
+incorporates the message (the plaintext) into the key.
+The key is generated from the message in some automated fashion,
+sometimes by selecting certain letters from the text or, more commonly,
+by adding a short primer key to the front of the message.
+"""
+
+
+def encrypt(plaintext: str, key: str) -> str:
+    """
+    Encrypt a given plaintext (string) and key (string), returning the
+    encrypted ciphertext.
+    >>> encrypt("hello world", "coffee")
+    'jsqqs avvwo'
+    >>> encrypt("coffee is good as python", "TheAlgorithms")
+    'vvjfpk wj ohvp su ddylsv'
+    >>> encrypt("coffee is good as python", 2)
+    Traceback (most recent call last):
+        ...
+    TypeError: key must be a string
+    >>> encrypt("", "TheAlgorithms")
+    Traceback (most recent call last):
+        ...
+    ValueError: plaintext is empty
+    """
+    if not isinstance(plaintext, str):
+        raise TypeError("plaintext must be a string")
+    if not isinstance(key, str):
+        raise TypeError("key must be a string")
+
+    if not plaintext:
+        raise ValueError("plaintext is empty")
+    if not key:
+        raise ValueError("key is empty")
+
+    key += plaintext
+    plaintext = plaintext.lower()
+    key = key.lower()
+    plaintext_iterator = 0
+    key_iterator = 0
+    ciphertext = ""
+    while plaintext_iterator < len(plaintext):
+        if (
+            ord(plaintext[plaintext_iterator]) < 97
+            or ord(plaintext[plaintext_iterator]) > 122
+        ):
+            ciphertext += plaintext[plaintext_iterator]
+            plaintext_iterator += 1
+        elif ord(key[key_iterator]) < 97 or ord(key[key_iterator]) > 122:
+            key_iterator += 1
+        else:
+            ciphertext += chr(
+                (
+                    (ord(plaintext[plaintext_iterator]) - 97 + ord(key[key_iterator]))
+                    - 97
+                )
+                % 26
+                + 97
+            )
+            key_iterator += 1
+            plaintext_iterator += 1
+    return ciphertext
+
+
+def decrypt(ciphertext: str, key: str) -> str:
+    """
+    Decrypt a given ciphertext (string) and key (string), returning the decrypted
+    ciphertext.
+    >>> decrypt("jsqqs avvwo", "coffee")
+    'hello world'
+    >>> decrypt("vvjfpk wj ohvp su ddylsv", "TheAlgorithms")
+    'coffee is good as python'
+    >>> decrypt("vvjfpk wj ohvp su ddylsv", "")
+    Traceback (most recent call last):
+        ...
+    ValueError: key is empty
+    >>> decrypt(527.26, "TheAlgorithms")
+    Traceback (most recent call last):
+        ...
+    TypeError: ciphertext must be a string
+    """
+    if not isinstance(ciphertext, str):
+        raise TypeError("ciphertext must be a string")
+    if not isinstance(key, str):
+        raise TypeError("key must be a string")
+
+    if not ciphertext:
+        raise ValueError("ciphertext is empty")
+    if not key:
+        raise ValueError("key is empty")
+
+    key = key.lower()
+    ciphertext_iterator = 0
+    key_iterator = 0
+    plaintext = ""
+    while ciphertext_iterator < len(ciphertext):
+        if (
+            ord(ciphertext[ciphertext_iterator]) < 97
+            or ord(ciphertext[ciphertext_iterator]) > 122
+        ):
+            plaintext += ciphertext[ciphertext_iterator]
+        else:
+            plaintext += chr(
+                (ord(ciphertext[ciphertext_iterator]) - ord(key[key_iterator])) % 26
+                + 97
+            )
+            key += chr(
+                (ord(ciphertext[ciphertext_iterator]) - ord(key[key_iterator])) % 26
+                + 97
+            )
+            key_iterator += 1
+        ciphertext_iterator += 1
+    return plaintext
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+    operation = int(input("Type 1 to encrypt or 2 to decrypt:"))
+    if operation == 1:
+        plaintext = input("Typeplaintext to be encrypted:\n")
+        key = input("Type the key:\n")
+        print(encrypt(plaintext, key))
+    elif operation == 2:
+        ciphertext = input("Type the ciphertext to be decrypted:\n")
+        key = input("Type the key:\n")
+        print(decrypt(ciphertext, key))
+    decrypt("jsqqs avvwo", "coffee")