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Fernet
======
.. currentmodule:: cryptography.fernet
.. testsetup::
import binascii
key = binascii.unhexlify(b"0" * 64)
`Fernet`_ is an implementation of symmetric (also known as "secret key")
authenticated cryptography. Fernet provides guarntees that a message encrypted
using it cannot be manipulated or read without the key.
.. class:: Fernet(key)
This class provides both encryption and decryption facilities.
.. doctest::
>>> from cryptography.fernet import Fernet
>>> f = Fernet(key)
>>> ciphertext = f.encrypt(b"my deep dark secret")
>>> ciphertext
'...'
>>> f.decrypt(ciphertext)
'my deep dark secret'
:param bytes key: A 32-byte key. This **must** be kept secret. Anyone with
this key is able to create and read messages.
.. method:: encrypt(plaintext)
:param bytes plaintext: The message you would like to encrypt.
:returns bytes: A secure message which cannot be read or altered
without the key. It is URL safe base64-encoded.
.. method:: decrypt(ciphertext, ttl=None)
:param bytes ciphertext: An encrypted message.
:param int ttl: Optionally, the number of seconds old a message may be
for it to be valid. If the message is older than
``ttl`` seconds (from the time it was originally
created) an exception will be raised. If ``ttl`` is not
provided (or is ``None``), the age of the message is
not considered.
:returns bytes: The original plaintext.
.. _`Fernet`: https://github.com/fernet/spec/
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