def create_policy(self, label: bytes, alice_privkey: UmbralPrivateKey,
bob_pubkey: UmbralPublicKey, policy_expiration, m: int,
n: int):
"""
Create a Policy with Alice granting Bob access to `label` DataSource
:param label: A label to represent the policies data
:param alice_privkey: Alice's private key
:param bob_pubkey: Bob's public key
:param policy_expiration: Datetime of policy expiration duration
:param m: Minimum number of KFrags needed to rebuild ciphertext
:param n: Total number of rekey shares to generate
:return: The policy granted to Bob
"""
# This is not how this should be implemented, but I am still figuring out
# the keying material and why it is randomly generated when a character is
# initialized, instead of being derived from the keys like the other powers
# or explained how it should be stored.
d = DelegatingPower()
d.umbral_keying_material = UmbralKeyingMaterial.from_bytes(
alice_privkey.to_bytes() + alice_privkey.get_pubkey().to_bytes())
# Initialize Alice
ALICE = Alice(
crypto_power_ups=[
SigningPower(keypair=SigningKeypair(alice_privkey)),
EncryptingPower(keypair=EncryptingKeypair(alice_privkey)),
# DelegatingPower
d
],
network_middleware=RestMiddleware(),
known_nodes=(self.ursula, ),
federated_only=True,
always_be_learning=True)
# Initialize Bob
BOB = Bob(crypto_power_ups=[
SigningPower(pubkey=bob_pubkey),
EncryptingPower(pubkey=bob_pubkey)
],
known_nodes=(self.ursula, ),
federated_only=True,
always_be_learning=True)
# Alice grants a policy for Bob
policy = ALICE.grant(BOB,
label,
m=m,
n=n,
expiration=policy_expiration)
return policy
ALICE = Alice(
network_middleware=RestMiddleware(),
known_nodes=(URSULA, ), # in lieu of seed nodes
federated_only=True,
always_be_learning=True) # TODO: 289
# Here are our Policy details.
policy_end_datetime = maya.now() + datetime.timedelta(days=5)
m = 2
n = 3
label = b"secret/files/and/stuff"
# Alice grants to Bob.
BOB = Bob(known_nodes=(URSULA, ), federated_only=True, always_be_learning=True)
ALICE.start_learning_loop(now=True)
policy = ALICE.grant(BOB, label, m=m, n=n, expiration=policy_end_datetime)
# Alice puts her public key somewhere for Bob to find later...
alices_pubkey_bytes_saved_for_posterity = bytes(ALICE.stamp)
# ...and then disappears from the internet.
del ALICE
# (this is optional of course - she may wish to remain in order to create
# new policies in the future. The point is - she is no longer obligated.
#####################
# some time passes. #
# ... #
# #
# ... #
# And now for Bob. #
