Implemented examples from https://docs.pushbullet.com/#end-to-end-encryption in python2/3 with python-cryptography (https://cryptography.io)

aes_gcm_encryption.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from __future__ import unicode_literals

from binascii import a2b_base64, b2a_base64
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.ciphers import (
	Cipher, algorithms, modes
)
import os

def generate_key():
	password = b"hunter2"
	salt = b"up0snaKOsn"

	pkdf = PBKDF2HMAC(
			algorithm=hashes.SHA256(), 
			length=32,
			salt=salt,
			iterations=30000,
			backend=default_backend())

	key = pkdf.derive(password)

	base64_key = b2a_base64(key)
	print("base64_key:", base64_key)

def encrypt():
	key = a2b_base64("1sW28zp7CWv5TtGjlQpDHHG4Cbr9v36fG5o4f74LsKg=")
	initialization_vector = os.urandom(12)
	message = "meow!"

	cipher = Cipher(
			algorithms.AES(key),
			modes.GCM(initialization_vector),
			backend=default_backend()
	).encryptor()
	
	encrypted_message = cipher.update(message.encode()) + cipher.finalize()
	# Must finalize encryption before getting tag
	tag = cipher.tag

	encoded_message = b"1" + tag + initialization_vector + encrypted_message
	base64_encoded_message = b2a_base64(encoded_message)
	print("base64_encoded_message:", base64_encoded_message)

def decrypt():
	key = a2b_base64("1sW28zp7CWv5TtGjlQpDHHG4Cbr9v36fG5o4f74LsKg=")
	encoded_message = a2b_base64("MSfJxxY5YdjttlfUkCaKA57qU9SuCN8+ZhYg/xieI+lDnQ==")

	version = encoded_message[0:1]
	tag = encoded_message[1:17]
	initialization_vector = encoded_message[17:29]
	encrypted_message = encoded_message[29:]

	if version != b"1":
		raise Exception("Invalid Version")

	decipher = Cipher(
					algorithms.AES(key),
					modes.GCM(initialization_vector, tag),
					backend=default_backend()
				).decryptor()

	message = decipher.update(encrypted_message) + decipher.finalize()
	message = message.decode()
	print("message:", message)

if __name__ == "__main__":
	generate_key()
	encrypt()
	decrypt()