.. hazmat::

Ed448 signing
=============

.. currentmodule:: cryptography.hazmat.primitives.asymmetric.ed448


Ed448 is an elliptic curve signing algorithm using `EdDSA`_.


Signing & Verification
~~~~~~~~~~~~~~~~~~~~~~

.. doctest::

    >>> from cryptography.hazmat.primitives.asymmetric.ed448 import Ed448PrivateKey
    >>> private_key = Ed448PrivateKey.generate()
    >>> signature = private_key.sign(b"my authenticated message")
    >>> public_key = private_key.public_key()
    >>> # Raises InvalidSignature if verification fails
    >>> public_key.verify(signature, b"my authenticated message")

Key interfaces
~~~~~~~~~~~~~~

.. class:: Ed448PrivateKey

    .. versionadded:: 2.6

    .. classmethod:: generate()

        Generate an Ed448 private key.

        :returns: :class:`Ed448PrivateKey`

    .. classmethod:: from_private_bytes(data)

        :param data: 57 byte private key.
        :type data: :term:`bytes-like`

        :returns: :class:`Ed448PrivateKey`

    .. method:: public_key()

        :returns: :class:`Ed448PublicKey`

    .. method:: sign(data)

        :param bytes data: The data to sign.

        :returns bytes: The 114 byte signature.

    .. method:: private_bytes(encoding, format, encryption_algorithm)

        Allows serialization of the key to bytes. Encoding (
        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.PEM`,
        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.DER`, or
        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`) and
        format (
        :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.PKCS8`
        or
        :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.Raw`
        ) are chosen to define the exact serialization.

        :param encoding: A value from the
            :class:`~cryptography.hazmat.primitives.serialization.Encoding` enum.

        :param format: A value from the
            :class:`~cryptography.hazmat.primitives.serialization.PrivateFormat`
            enum. If the ``encoding`` is
            :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`
            then ``format`` must be
            :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.Raw`
            , otherwise it must be
            :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.PKCS8`.

        :param encryption_algorithm: An instance of an object conforming to the
            :class:`~cryptography.hazmat.primitives.serialization.KeySerializationEncryption`
            interface.

        :return bytes: Serialized key.

.. class:: Ed448PublicKey

    .. versionadded:: 2.6

    .. classmethod:: from_public_bytes(data)

        :param bytes data: 57 byte public key.

        :returns: :class:`Ed448PublicKey`

    .. method:: public_bytes(encoding, format)

        Allows serialization of the key to bytes. Encoding (
        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.PEM`,
        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.DER`, or
        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`) and
        format (
        :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.SubjectPublicKeyInfo`
        or
        :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.Raw`
        ) are chosen to define the exact serialization.

        :param encoding: A value from the
            :class:`~cryptography.hazmat.primitives.serialization.Encoding` enum.

        :param format: A value from the
            :class:`~cryptography.hazmat.primitives.serialization.PublicFormat`
            enum. If the ``encoding`` is
            :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`
            then ``format`` must be
            :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.Raw`
            , otherwise it must be
            :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.SubjectPublicKeyInfo`.

        :returns bytes: The public key bytes.

    .. method:: verify(signature, data)

        :param bytes signature: The signature to verify.

        :param bytes data: The data to verify.

        :raises cryptography.exceptions.InvalidSignature: Raised when the
            signature cannot be verified.


.. _`EdDSA`: https://en.wikipedia.org/wiki/EdDSA