Trust Propagation

Trust propagation in the Local Protocol allows trust to spread across the network based on transaction history and graph connectivity. The concept ensures that trust diminishes gradually as it travels further from a trusted source node, enabling the protocol to assess participant reliability over time.

This mechanism helps the network establish broader trust networks, making it harder for malicious actors to gain undue influence without genuine connectivity.

Key Concepts#

• Decaying Trust: Trust assumptions weaken over longer paths from the source.
• Network-Wide Impact: Trust spreads through the transaction graph, enhancing overall reliability.

Trust as Boosts to EC#

The boost in eigenvector centrality (EC) resulting from any proof—be it an identity proof or a service proof—doesn't just affect the individual node or transaction; it propagates through the network due to the recursive nature of the EC calculation. Nodes directly connected to the node or edge associated with the proof will also see an increase in their EC because their centrality depends on the centrality of their neighbors.

The effect of any proof diminishes exponentially over longer paths in the graph. The modified EC calculation naturally captures this phenomenon, as the solution to the inhomogeneous eigenvalue problem (more on this later) accounts for the additional trust introduced by the proofs (the doping vector for nodes or adjusted weights for edges).

You can visualize the network as a series of concentric circles centered around the node or edge that has incorporated a proof. The nodes directly connected form the first circle; these are the immediate neighbors who have direct interactions with the proof-bearing node or transaction. The second circle consists of nodes connected to those immediate neighbors, which are two steps away, and so on for subsequent circles. The influence of the proof's boost in eigenvector centrality is strongest at the center and decreases exponentially as you move outward.

Nodes that transact with those who have submitted proofs benefit more than they would have without the proofs. This results in higher rewards for both parties and increases their attractiveness as transaction partners in the network. In this way, nodes in the network might view the submission of proofs, and thus the increase in security for the network, as an investment in their EC. When self-interested actors perform actions that have positive security externalities, we achieve strong design properties.

Next Steps#

In the next section, we will examine Sampling & Slashing, a mechanism for probabilistic verification and penalization.