8.9 KiB
Getting Started with Characters
A Note about Side Channels
The NuCypher network does not store or handle an application's data; instead - it manages access to application data. Management of encrypted secrets and public keys tends to be highly domain-specific - The surrounding architecture will vary greatly depending on the throughput, sensitivity, and sharing cadence of application secrets. In all cases, NuCypher must be integrated with a storage and transport layer in order to function properly. Along with the transport of ciphertexts, a nucypher application also needs to include channels for Alice and Bob to discover each other's public keys, and provide policy encrypting information to Bob and Enrico.
Side Channel Application Data
- Secrets:
- Message Kits - Encrypted Messages, or "Ciphertexts"
- Identities:
- Alice Verifying Key - Public key used for verifying Alice
- Bob Encrypting Key - Public key used to encrypt for Bob
- Bob Verifying Key - Public key used to verify Bob
- Policies:
- Policy Encrypting Key - Public key used to encrypt messages for a Policy.
- Labels - A label for specifying a Policy's target, like a filepath
Running an Ethereum Node
Operation of a decentralized NuCypher character [Alice, Bob, Ursula] requires
a connection to an Ethereum node and wallet to interact with smart
contracts (https://docs.nucypher.com/en/latest/architecture/contracts.html).
For general background information about choosing a node technology and operation, see https://web3py.readthedocs.io/en/stable/node.html.
In this guide, a local Geth node connected to the Goerli Testnet is used. For detailed information on using the geth CLI and Javascript console, see https://geth.ethereum.org/interface/Command-Line-Options.
To run a Goerli-connected Geth node in fast syncing mode:
$ geth --goerli
To run a Goerli-connected Geth node in light syncing mode:
$ geth --goerli --syncmode light
Note that using --syncmode light is not 100% stable but can be a life savior when using
a mobile connection (or congested hackathon wifi...).
Connect to the Geth Console to test your ethereum node's IPC:
$ geth attach ~/.ethereum/goerli/geth.ipc
Wallets
To list available accounts on your geth node (Hardware wallet addresses will also be listed here if one is attached to the system hardware):
$ geth attach ~/.ethereum/goerli/geth.ipc
> eth.accounts
["0x287a817426dd1ae78ea23e9918e2273b6733a43d"]
To create a new software based Geth account:
$ geth attach ~/.ethereum/goerli/geth.ipc
> personal.newAccount()
...
"0xc080708026a3a280894365efd51bb64521c45147"
Note that the Geth console does not return EIP-55 compliant checksum addresses, and instead will output the lowercase version of the address. Since Nucypher requires EIP-55 checksum addresses, you will need to convert your address to checksum format:
> web3.toChecksumAddress(eth.accounts[0])
"0x287A817426DD1AE78ea23e9918e2273b6733a43D"
Connecting to The NuCypher Network
Provider URI
Nucypher uses the ethereum node's IPC-File to communicate, specified by provider_uri.
By default in ubuntu, the path is ~/.ethereum/goerli/geth.ipc - This path
will also be logged to the geth-running console on startup.
Connecting Nucypher to an Ethereum Provider
from nucypher.blockchain.eth.interfaces import BlockchainInterfaceFactory
BlockchainInterfaceFactory.initialize_interface(provider_uri='~/.ethereum/goerli/geth.ipc')
Ursula: Untrusted Re-Encryption Proxies
When initializing an Alice, Bob, or Ursula, an initial "Stranger-Ursula" is needed to perform
the role of a Teacher, or "seednode":
from nucypher.characters.lawful import Ursula
seed_uri = "discover.nucypher.network:9151"
seed_uri2 = "104.248.215.144:9151"
ursula = Ursula.from_seed_and_stake_info(seed_uri=seed_uri)
another_ursula = Ursula.from_seed_and_stake_info(seed_uri=seed_uri2)
Stranger Ursulas can be created by invoking the from_seed_and_stake_info method, then a list of known_nodes
can be passed into any Character's init. The known_nodes will inform your character of all of the nodes
they know about network-wide, then kick-off the automated node-discovery loop:
from nucypher.characters.lawful import Alice
alice = Alice(known_nodes=[ursula, another_ursula], ...)
For information on how to run a staking Ursula node via CLI, see https://docs.nucypher.com/en/latest/guides/staking_guide.html
Alice: Grant Access to a Secret
Setup Alice
Create a NuCypher Keyring
from nucypher.config import NucypherKeyring
keyring = NucypherKeyring.generate(checksum_address='0x287A817426DD1AE78ea23e9918e2273b6733a43D', password=PASSWORD)
from nucypher.characters.lawful import Alice, Ursula
ursula = Ursula.from_seed_and_stake_info(seed_uri='discover.nucypher.network:9151')
# Unlock Alice's Keyring
keyring = NucypherKeyring(account='0x287A817426DD1AE78ea23e9918e2273b6733a43D')
keyring.unlock(password=PASSWORD)
# Instantiate Alice
alice = Alice(keyring=keyring, known_nodes=[ursula], provider_uri='~/.ethereum/goerli/geth.ipc')
# Start Node Discovery
alice.start_learning_loop(now=True)
Alice needs to know about Bob in order to grant access by acquiring Bob's public key's through the application side channel:
from umbral.keys import UmbralPublicKey
verifying_key = UmbralPublicKey.from_hex(verifying_key),
encrypting_key = UmbralPublicKey.from_hex(encryption_key)
Grant
Then, Alice can grant access to Bob:
from nucypher.characters.lawful import Bob
from datetime import timedelta
import maya
bob = Bob.from_public_keys(verifying_key=bob_verifying_key, encrypting_key=bob_encrypting_key)
policy_end_datetime = maya.now() + timedelta(days=5) # Five days from now
policy = alice.grant(bob,
label=b'my-secret-stuff', # Sent to Bob via side channel
m=2, n=3,
expiration=policy_end_datetime)
policy_encrypting_key = policy.public_key
Enrico: Encrypt a Secret
Setup Enrico
First, A policy_encrypting_key must be retrieved from the application side channel, then
to encrypt a secret using Enrico:
Encrypt
from nucypher.characters.lawful import Enrico
enrico = Enrico(policy_encrypting_key=policy_encrypting_key)
ciphertext, signature = enrico.encrypt_message(message=b'Peace at dawn.')
The ciphertext can then be sent to Bob via the application side channel.
Note that Alice can get the public key even before creating the policy. From this moment on, any Data Source (Enrico) that knows the public key can encrypt data originally intended for Alice, but can be shared with any Bob that Alice grants access.
policy_pubkey = alice.get_policy_encrypting_key_from_label(label)
Bob: Decrypt a Secret
For Bob to retrieve a secret, The ciphertext, label, policy encrypting key, and Alice's veryfying key must all be fetched from the application side channel. Then, Bob constructs his perspective of the policy's network actors:
Setup Bob
from nucypher.characters.lawful import Alice, Bob, Enrico, Ursula
# Application Side-Channel
# --------------------------
# label = <Side Channel>
# ciphertext = <Side Channel>
# policy_encrypting_key = <Side Channel>
# alice_verifying_key = <Side Channel>
# Everyone!
ursula = Ursula.from_seed_and_stake_info(seed_uri='discover.nucypher.network:9151')
alice = Alice.from_public_keys(verifying_key=alice_verifying_key)
enrico = Enrico(policy_encrypting_key=policy_encrypting_key)
# Generate and unlock Bob's keyring
keyring = NucypherKeyring.generate(checksum_address='0xC080708026a3A280894365Efd51Bb64521c45147', password=PASSWORD)
keyring.unlock(PASSWORD)
# Make Bob
bob = Bob(known_nodes=[ursula], checksum_address="0xC080708026a3A280894365Efd51Bb64521c45147")
Join a Policy
Next, Bob needs to join the policy:
bob.join_policy(label=label, alice_verifying_key=alice.public_keys(SigningPower), block=True)
Retrieve and Decrypt
Then Bob can retrieve, and decrypt the ciphertext:
cleartexts = bob.retrieve(label=label,
message_kit=ciphertext,
data_source=enrico,
alice_verifying_key=alice.public_keys(SigningPower))