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Filename : KMAC256.py
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# Copyright (c) 2021, Legrandin <helderijs@gmail.com>
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from Crypto.Util.py3compat import is_bytes

from .KMAC128 import KMAC_Hash
from . import cSHAKE256


def new(**kwargs):
    """Create a new KMAC256 object.

    Args:
        key (bytes/bytearray/memoryview):
            The key to use to compute the MAC.
            It must be at least 256 bits long (32 bytes).
        data (bytes/bytearray/memoryview):
            Optional. The very first chunk of the message to authenticate.
            It is equivalent to an early call to :meth:`KMAC_Hash.update`.
        mac_len (integer):
            Optional. The size of the authentication tag, in bytes.
            Default is 64. Minimum is 8.
        custom (bytes/bytearray/memoryview):
            Optional. A customization byte string (``S`` in SP 800-185).

    Returns:
        A :class:`KMAC_Hash` hash object
    """

    key = kwargs.pop("key", None)
    if not is_bytes(key):
        raise TypeError("You must pass a key to KMAC256")
    if len(key) < 32:
        raise ValueError("The key must be at least 256 bits long (32 bytes)")

    data = kwargs.pop("data", None)

    mac_len = kwargs.pop("mac_len", 64)
    if mac_len < 8:
        raise ValueError("'mac_len' must be 8 bytes or more")

    custom = kwargs.pop("custom", b"")

    if kwargs:
        raise TypeError("Unknown parameters: " + str(kwargs))

    return KMAC_Hash(data, key, mac_len, custom, "20", cSHAKE256, 136)