1  # The MIT License (MIT)
 2  #
 3  # Copyright (c) 2020 Jim Bennett
 4  #
 5  # Permission is hereby granted, free of charge, to any person obtaining a copy
 6  # of this software and associated documentation files (the "Software"), to deal
 7  # in the Software without restriction, including without limitation the rights
 8  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9  # copies of the Software, and to permit persons to whom the Software is
10  # furnished to do so, subject to the following conditions:
11  #
12  # The above copyright notice and this permission notice shall be included in
13  # all copies or substantial portions of the Software.
14  #
15  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21  # THE SOFTWARE.
22  """Computes a derived symmetric key from a secret and a message
23  :param str secret: The secret to use for the key
24  :param str msg: The message to use for the key
25  :returns: The derived symmetric key
26  :rtype: bytes
27  """
28  
29  from .base64 import b64decode, b64encode
30  from .hmac import new_hmac
31  
32  
33  def compute_derived_symmetric_key(secret: str, msg: str) -> bytes:
34      """Computes a derived symmetric key from a secret and a message
35      :param str secret: The secret to use for the key
36      :param str msg: The message to use for the key
37      :returns: The derived symmetric key
38      :rtype: bytes
39      """
40      return b64encode(new_hmac(b64decode(secret), msg=msg.encode("utf8")).digest())