Owner: @Marcin Pawlowski

Reviewers: 🟢@Álvaro Castro-Castilla

Broadcasting

In this section we are analyzing the security (information leakage) of the mix network that is using broadcasting channel for inter-node communication. In other words, we are assuming that nodes do not contact each other directly for the purposes of mixing, and every message that is send by a node to the network is delivered to all other nodes.

Models

Let us start from defining simple models that will be used for further analysis.

Broadcasting Model

We are defining a broadcasting model as a combination of two network level functions that are implemented by each node.

• Send is defined as an initial messaging event, the one that starts broadcasting a new message.
• Relay is defined as a messaging event that resends (rebroadcasts) the message to the network.

Broadcasting Mixing Model

Now let us allow the Node B to mix the traffic, this is done through the following function.

• Mix is defined as an internal node operation where an incoming message (where Node B is its recipient) is modified by the node and send to the network.

General Mixing Model

Let us now focus on a general mixing model. Let us assume that a node always relays messages regardless if he is recipient or not, then we can safely abstract from the underlying communication mechanism and introduce the following model that consists of the next functions.

• Receive is a function that enables a node to collect messages from the network that are mixed by the node.
• Send is a function that enables a node to send (broadcast) mixed messages.
• Mix is a internal function that enables a node to mix the messages.