WIP: Mixnet: Update spec for NomMix

mixnet/config.py

@@ -2,110 +2,56 @@
 
 import random
 from dataclasses import dataclass
-from typing import List, TypeAlias
+from typing import List
 
 from cryptography.hazmat.primitives.asymmetric.x25519 import (
     X25519PrivateKey,
     X25519PublicKey,
 )
-from pysphinx.node import Node
-
-from mixnet.bls import BlsPrivateKey, BlsPublicKey
-from mixnet.fisheryates import FisherYates
+from pysphinx.sphinx import Node as SphinxNode
 
 
 @dataclass
 class MixnetConfig:
-    topology_config: MixnetTopologyConfig
-    mixclient_config: MixClientConfig
-    mixnode_config: MixNodeConfig
+    node_configs: List[NodeConfig]
+    membership: MixMembership
 
 
 @dataclass
-class MixnetTopologyConfig:
-    mixnode_candidates: List[MixNodeInfo]
-    size: MixnetTopologySize
-    entropy: bytes
+class NodeConfig:
+    private_key: X25519PrivateKey
+    transmission_rate_per_sec: int  # Global Transmission Rate
 
 
 @dataclass
-class MixClientConfig:
-    emission_rate_per_min: int  # Poisson rate parameter: lambda
-    redundancy: int
-    topology: MixnetTopology
-
-
-@dataclass
-class MixNodeConfig:
-    encryption_private_key: X25519PrivateKey
-    delay_rate_per_min: int  # Poisson rate parameter: mu
-
-
-@dataclass
-class MixnetTopology:
-    # In production, this can be a 1-D array, which is accessible by indexes.
-    # Here, we use a 2-D array for readability.
-    layers: List[List[MixNodeInfo]]
-
-    def __init__(
-        self,
-        config: MixnetTopologyConfig,
-    ) -> None:
-        """
-        Build a new topology deterministically using an entropy and a given set of candidates.
-        """
-        shuffled = FisherYates.shuffle(config.mixnode_candidates, config.entropy)
-        sampled = shuffled[: config.size.num_total_mixnodes()]
-
-        layers = []
-        for layer_id in range(config.size.num_layers):
-            start = layer_id * config.size.num_mixnodes_per_layer
-            layer = sampled[start : start + config.size.num_mixnodes_per_layer]
-            layers.append(layer)
-        self.layers = layers
+class MixMembership:
+    nodes: List[NodeInfo]
 
-    def generate_route(self, mix_destination: MixNodeInfo) -> list[MixNodeInfo]:
+    def generate_route(self, num_hops: int, last_mix: NodeInfo) -> list[NodeInfo]:
         """
         Generate a mix route for a Sphinx packet.
         The pre-selected mix_destination is used as a last mix node in the route,
         so that associated packets can be merged together into a original message.
         """
-        route = [random.choice(layer) for layer in self.layers[:-1]]
-        route.append(mix_destination)
+        route = [self.choose() for _ in range(num_hops - 1)]
+        route.append(last_mix)
         return route
 
-    def choose_mix_destination(self) -> MixNodeInfo:
+    def choose(self) -> NodeInfo:
         """
-        Choose a mix node from the last mix layer as a mix destination
-        that will reconstruct a message from Sphinx packets.
+        Choose a mix node as a mix destination that will reconstruct a message from Sphinx packets.
         """
-        return random.choice(self.layers[-1])
+        return random.choice(self.nodes)
 
 
 @dataclass
-class MixnetTopologySize:
-    num_layers: int
-    num_mixnodes_per_layer: int
-
-    def num_total_mixnodes(self) -> int:
-        return self.num_layers * self.num_mixnodes_per_layer
-
-
-# 32-byte that represents an IP address and a port of a mix node.
-NodeAddress: TypeAlias = bytes
-
-
-@dataclass
-class MixNodeInfo:
-    identity_private_key: BlsPrivateKey
-    encryption_private_key: X25519PrivateKey
-    addr: NodeAddress
-
-    def identity_public_key(self) -> BlsPublicKey:
-        return self.identity_private_key.get_g1()
+class NodeInfo:
+    private_key: X25519PrivateKey
 
-    def encryption_public_key(self) -> X25519PublicKey:
-        return self.encryption_private_key.public_key()
+    def public_key(self) -> X25519PublicKey:
+        return self.private_key.public_key()
 
-    def sphinx_node(self) -> Node:
-        return Node(self.encryption_private_key, self.addr)
+    def sphinx_node(self) -> SphinxNode:
+        # TODO: Use a pre-signed incentive tx, instead of NodeAddress
+        dummy_node_addr = bytes(32)
+        return SphinxNode(self.private_key, dummy_node_addr)