add weights for real_message_prob

mixnet/v2/sim/config.py

@@ -10,9 +10,17 @@ class Config:
     running_time: int
     num_nodes: int
     num_mix_layers: int
+    # An interval of sending a new real/cover message
+    # A probability of actually sending a message depends on the following parameters.
     message_interval: int
-    real_message_prob: float  # TODO: should be proportional to its stake
+    # A probability of sending a real message within one cycle
+    real_message_prob: float
+    # A weight of real message emission probability of some nodes
+    # The length of the list should be <= num_nodes.
+    real_message_prob_weights: list[float]
+    # A probability of sending a cover message within one cycle if not sending a real message
     cover_message_prob: float
+    # A maximum preparation time (delay) before sending the message
     max_message_prep_time: float
 
     @classmethod
@@ -26,9 +34,11 @@ class Config:
         assert config.num_nodes > 0
         assert 0 < config.num_mix_layers <= config.num_nodes
         assert config.message_interval > 0
-        assert config.real_message_prob >= 0
+        assert config.real_message_prob > 0
+        assert len(config.real_message_prob_weights) <= config.num_nodes
+        for weight in config.real_message_prob_weights:
+            assert weight >= 1
         assert config.cover_message_prob >= 0
-        assert config.real_message_prob + config.cover_message_prob <= 1
         assert config.max_message_prep_time >= 0
 
         return config

mixnet/v2/sim/config.yaml

@@ -1,9 +1,15 @@
 running_time: 30
 num_nodes: 100
 num_mix_layers: 3
+# An interval of sending a new real/cover message
+# A probability of actually sending a message depends on the following parameters.
 message_interval: 1
-# (real_message_prob + cover_message_prob) should be <= 1
-# If the sum is < 1, then the remaining probability is for sending nothing.
-real_message_prob: 0.01
+# A probability of sending a real message within a cycle
+real_message_prob: 0.1
+# A weight of real message emission probability of some nodes
+# The length of the list should be <= num_nodes.
+real_message_prob_weights: [10, 8, 12]
+# A probability of sending a cover message within a cycle if not sending a real message
 cover_message_prob: 0.2
+# A maximum preparation time (delay) before sending the message
 max_message_prep_time: 0.3

mixnet/v2/sim/node.py

@@ -44,13 +44,18 @@ class Node:
 
     def payload_to_send(self) -> bytes | None:
         rnd = random.random()
-        if rnd < self.config.real_message_prob:
+        if rnd < self.real_message_prob():
             return self.REAL_PAYLOAD
-        elif rnd < self.config.real_message_prob + self.config.cover_message_prob:
+        elif rnd < self.config.cover_message_prob:
             return self.COVER_PAYLOAD
         else:
             return None
 
+    def real_message_prob(self):
+        weight = self.config.real_message_prob_weights[self.id] \
+            if self.id < len(self.config.real_message_prob_weights) else 0
+        return self.config.real_message_prob * weight
+
     def create_message(self, payload: bytes) -> SphinxPacket:
         """
         Creates a message using the Sphinx format