added aes-128 algorithm in ciphers

ciphers/aes_128.py

@@ -0,0 +1,61 @@
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+import base64
+
+def aes_encrypt(plaintext: str, key: str) -> str:
+    """
+    AES-128 Encryption using CBC mode and PKCS7 padding.
+
+    :param plaintext: The plaintext message to be encrypted.
+    :param key: The encryption key (16 characters = 128 bits).
+    :return: Encrypted message (Base64 encoded).
+
+    >>> msg = "This is a secret message."
+    >>> key = "thisisaverysecret"
+    >>> enc = aes_encrypt(msg, key)
+    >>> dec = aes_decrypt(enc, key)
+    >>> aes_decrypt(enc, key) == msg
+    True
+    """
+    cipher = AES.new(key.encode('utf-8'), AES.MODE_CBC)
+    ciphertext = cipher.encrypt(pad(plaintext.encode('utf-8'), AES.block_size))
+    return base64.b64encode(cipher.iv + ciphertext).decode('utf-8')
+
+def aes_decrypt(ciphertext: str, key: str) -> str:
+    """
+    AES-128 Decryption using CBC mode and PKCS7 padding.
+
+    :param ciphertext: The Base64 encoded encrypted message.
+    :param key: The decryption key (16 characters = 128 bits).
+    :return: Decrypted plaintext message.
+
+    >>> msg = "This is a secret message."
+    >>> key = "thisisaverysecret"
+    >>> enc = aes_encrypt(msg, key)
+    >>> dec = aes_decrypt(enc, key)
+    >>> dec == msg
+    True
+    """
+    raw = base64.b64decode(ciphertext)
+    cipher = AES.new(key.encode('utf-8'), AES.MODE_CBC, iv=raw[:AES.block_size])
+    return unpad(cipher.decrypt(raw[AES.block_size:]), AES.block_size).decode('utf-8')
+
+def main() -> None:
+    key = input("Enter 16-character key (AES-128): ")
+    if len(key) != 16:
+        raise ValueError("Key must be 16 characters long!")
+
+    message = input("Enter message: ")
+
+    # Encryption
+    encrypted_message = aes_encrypt(message, key)
+    print("Encrypted message:", encrypted_message)
+
+    # Decryption
+    decrypted_message = aes_decrypt(encrypted_message, key)
+    print("Decrypted message:", decrypted_message)
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
+    main()