Background

Please refer to Nomos Blend Network: Introduction [WIP Design] for more information about the Nomos Mix design.

Introduction

The Cryptographic Mix protocol enables nodes to send a message that, after a cryptographic operation performed by mix node, cannot be linked back to the sender. The protocol works as follows.

The node selects $k$ nodes from the set of all nodes $N$, these nodes are going to take part in cryptographic mixing. That is, a message $m$ is encrypted with key $\kappa_i$ where $i \in {\{1,...,k\}}$ and is a keying material for each node in the set of $k$ nodes. Then, the message is encrypted multiple times $m^k =E{{\kappa_1}}(…(E{{\kappa_k}}(m))...)$ forming an encrypted chain which can be only decrypted by the (ordered) set of selected cryptographic mixing nodes.

The leader node sends the message $m^k$ to the network. The node $i=1$ receives the message $m^k$ and decrypts $m^k$ and receives $m^{k-1} =E{{\kappa_2}}(…(E{{\kappa_{k}}}(m))...)$. Then the $m^{k-1}$ message is gossiped to the next node, until the last decryption by node $k$ which reveals the message $m$. The node $k$ broadcasts the message $m$.

The Cryptographic Mix gives the the following properties.

The external observer of a node cannot link the incoming message to the outgoing message based on the observation of the construction of messages.
The local observer (controlling nodes executing cryptographic mixing) cannot link the incoming to outgoing message when at least one node performing the mixing is an honest node.

Design

NOMIX-Architecture-3tiers-Copy of Page-8.png

Below is a version where the relayer is handling Data Messages.