112 lines
3.1 KiB
Python
112 lines
3.1 KiB
Python
from __future__ import annotations
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import random
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from dataclasses import dataclass
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from typing import List, TypeAlias
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from cryptography.hazmat.primitives.asymmetric.x25519 import (
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X25519PrivateKey,
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X25519PublicKey,
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)
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from pysphinx.node import Node
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from mixnet.bls import BlsPrivateKey, BlsPublicKey
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from mixnet.fisheryates import FisherYates
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@dataclass
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class MixnetConfig:
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topology_config: MixnetTopologyConfig
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mixclient_config: MixClientConfig
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mixnode_config: MixNodeConfig
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@dataclass
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class MixnetTopologyConfig:
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mixnode_candidates: List[MixNodeInfo]
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size: MixnetTopologySize
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entropy: bytes
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@dataclass
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class MixClientConfig:
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emission_rate_per_min: int # Poisson rate parameter: lambda
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redundancy: int
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topology: MixnetTopology
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@dataclass
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class MixNodeConfig:
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encryption_private_key: X25519PrivateKey
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delay_rate_per_min: int # Poisson rate parameter: mu
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@dataclass
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class MixnetTopology:
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# In production, this can be a 1-D array, which is accessible by indexes.
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# Here, we use a 2-D array for readability.
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layers: List[List[MixNodeInfo]]
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def __init__(
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self,
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config: MixnetTopologyConfig,
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) -> None:
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"""
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Build a new topology deterministically using an entropy and a given set of candidates.
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"""
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shuffled = FisherYates.shuffle(config.mixnode_candidates, config.entropy)
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sampled = shuffled[: config.size.num_total_mixnodes()]
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layers = []
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for layer_id in range(config.size.num_layers):
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start = layer_id * config.size.num_mixnodes_per_layer
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layer = sampled[start : start + config.size.num_mixnodes_per_layer]
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layers.append(layer)
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self.layers = layers
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def generate_route(self, mix_destination: MixNodeInfo) -> list[MixNodeInfo]:
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"""
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Generate a mix route for a Sphinx packet.
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The pre-selected mix_destination is used as a last mix node in the route,
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so that associated packets can be merged together into a original message.
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"""
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route = [random.choice(layer) for layer in self.layers[:-1]]
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route.append(mix_destination)
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return route
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def choose_mix_destination(self) -> MixNodeInfo:
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"""
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Choose a mix node from the last mix layer as a mix destination
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that will reconstruct a message from Sphinx packets.
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"""
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return random.choice(self.layers[-1])
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@dataclass
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class MixnetTopologySize:
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num_layers: int
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num_mixnodes_per_layer: int
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def num_total_mixnodes(self) -> int:
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return self.num_layers * self.num_mixnodes_per_layer
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# 32-byte that represents an IP address and a port of a mix node.
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NodeAddress: TypeAlias = bytes
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@dataclass
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class MixNodeInfo:
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identity_private_key: BlsPrivateKey
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encryption_private_key: X25519PrivateKey
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addr: NodeAddress
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def identity_public_key(self) -> BlsPublicKey:
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return self.identity_private_key.get_g1()
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def encryption_public_key(self) -> X25519PublicKey:
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return self.encryption_private_key.public_key()
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def sphinx_node(self) -> Node:
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return Node(self.encryption_private_key, self.addr)
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