text: # Copyright 2014 Google Inc. All rights reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import adb_protocol
  
  from cryptography.hazmat.backends import default_backend
  from cryptography.hazmat.primitives import hashes
  from cryptography.hazmat.primitives import serialization
  from cryptography.hazmat.primitives.asymmetric import padding
  from cryptography.hazmat.primitives.asymmetric import utils
  
  
  class CryptographySigner(adb_protocol.AuthSigner):
      """AuthSigner using cryptography.io."""
  
      def __init__(self, rsa_key_path):
          with open(rsa_key_path + '.pub') as rsa_pub_file:
              self.public_key = rsa_pub_file.read()
  
          with open(rsa_key_path) as rsa_prv_file:
              self.rsa_key = serialization.load_pem_private_key(
                      rsa_prv_file.read(), None, default_backend())
  
      def Sign(self, data):
          return self.rsa_key.sign(
              data, padding.PKCS1v15(), utils.Prehashed(hashes.SHA1()))
  
      def GetPublicKey(self):
          return self.public_key
  