Concise demo for Prague meetup.

examples/finnegans-wake-concise-demo.py

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+# This is an example of Alice setting a Policy on the NuCypher network.
+# In this example, Alice uses n=3.
+
+# WIP w/ hendrix@3.1.0
+
+import datetime
+import os
+import shutil
+import sys
+
+import maya
+from twisted.logger import ILogObserver
+from twisted.logger import globalLogPublisher
+from umbral.keys import UmbralPublicKey
+######################
+# Boring setup stuff #
+######################
+from zope.interface import provider
+
+from nucypher.characters.lawful import Alice, Bob, Ursula
+from nucypher.config.constants import SeednodeMetadata
+from nucypher.data_sources import DataSource as Enrico
+# This is already running in another process.
+from nucypher.network.middleware import RestMiddleware
+
+
+@provider(ILogObserver)
+def simpleObserver(event):
+    print(event)
+
+globalLogPublisher.addObserver(simpleObserver)
+
+# Temporary storage area for demo
+SHARED_CRUFTSPACE = "{}/examples-runtime-cruft".format(os.path.dirname(os.path.abspath(__file__)))
+CRUFTSPACE = "{}/finnegans-wake-demo".format(SHARED_CRUFTSPACE)
+CERTIFICATE_DIR = "{}/certs".format(CRUFTSPACE)
+shutil.rmtree(CRUFTSPACE, ignore_errors=True)
+os.mkdir(CRUFTSPACE)
+os.mkdir(CERTIFICATE_DIR)
+
+
+#######################################
+# Finnegan's Wake on NuCypher Testnet #
+# (will fail with bad connection) #####
+#######################################
+
+TESTNET_LOAD_BALANCER = "eu-federated-balancer-40be4480ec380cd7.elb.eu-central-1.amazonaws.com"
+
+##############################################
+# Ursula, the Untrusted Re-Encryption Proxy  #
+##############################################
+ursula = Ursula.from_seed_and_stake_info(host=TESTNET_LOAD_BALANCER,
+                                         certificates_directory=CERTIFICATE_DIR,
+                                         federated_only=True,
+                                         minimum_stake=0)
+
+# 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, the Authority of the Policy #
+######################################
+
+ALICE = Alice(network_middleware=RestMiddleware(),
+              known_nodes=[ursula],
+              learn_on_same_thread=True,
+              federated_only=True,
+              known_certificates_dir=CERTIFICATE_DIR,
+              )
+
+BOB = Bob(
+    known_nodes=[ursula],
+    network_middleware=RestMiddleware(),
+    federated_only=True,
+    start_learning_now=True,
+    learn_on_same_thread=True,
+    known_certificates_dir=CERTIFICATE_DIR)
+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
+
+#####################
+# some time passes. #
+# ...               #
+#                   #
+# ...               #
+# And now for Bob.  #
+#####################
+
+#####################
+# Bob the BUIDLer  ##
+#####################
+BOB.join_policy(label, alices_pubkey_bytes_saved_for_posterity)
+
+# Now that Bob has joined the Policy, let's show how Enrico the Encryptor
+# can share data with the members of this Policy and then how Bob retrieves it.
+finnegans_wake = open(sys.argv[1], 'rb')
+
+print()
+print("**************James Joyce's Finnegan's Wake**************")
+print()
+print("---------------------------------------------------------")
+
+for counter, plaintext in enumerate(finnegans_wake):
+
+    #########################
+    # Enrico, the Encryptor #
+    #########################
+    enciro = Enrico(policy_pubkey_enc=policy.public_key)
+
+    # In this case, the plaintext is a
+    # single passage from James Joyce's Finnegan's Wake.
+    # The matter of whether encryption makes the passage more or less readable
+    # is left to the reader to determine.
+    single_passage_ciphertext, _signature = enciro.encapsulate_single_message(plaintext)
+    data_source_public_key = bytes(enciro.stamp)
+    del enciro
+
+    ###############
+    # Back to Bob #
+    ###############
+
+    enrico_as_understood_by_bob = Enrico.from_public_keys(
+        policy_public_key=policy.public_key,
+        datasource_public_key=data_source_public_key,
+        label=label
+    )
+
+    # Now Bob can retrieve the original message.
+    alice_pubkey_restored_from_ancient_scroll = UmbralPublicKey.from_bytes(alices_pubkey_bytes_saved_for_posterity)
+    delivered_cleartexts = BOB.retrieve(message_kit=single_passage_ciphertext,
+                                        data_source=enrico_as_understood_by_bob,
+                                        alice_verifying_key=alice_pubkey_restored_from_ancient_scroll)
+
+    # We show that indeed this is the passage originally encrypted by Enrico.
+    assert plaintext == delivered_cleartexts[0]
+    print("Retrieved: {}".format(delivered_cleartexts[0]))