What is PoI (Proof of Importance) and how to calculate it?

PoI rewards NEM network nodes based on currency held, transaction activity, and connectivity, encouraging active participation and reducing centralization.

Apr 08, 2025 at 10:49 am

What is PoI (Proof of Importance) and how to calculate it?

Proof of Importance (PoI) is a consensus mechanism used in certain blockchain networks, most notably by the NEM (New Economy Movement) cryptocurrency. Unlike Proof of Work (PoW) or Proof of Stake (PoS), which focus on computational power or the amount of cryptocurrency held, PoI aims to reward users based on their overall contribution to the network. This article will delve into the concept of PoI and provide a detailed explanation of how it is calculated.

Understanding Proof of Importance

PoI is designed to encourage active participation and engagement within the network. It measures the "importance" of a node based on several factors, including the amount of currency held, the number of transactions made, and the node's connectivity to other nodes. The goal is to create a more equitable system where users who contribute more to the network are rewarded more significantly.

In the NEM network, PoI is used to select which nodes will be allowed to harvest (generate) new blocks. Nodes with a higher importance score have a greater chance of being chosen to add a new block to the blockchain, thus earning the associated rewards.

Key Components of PoI

To understand how PoI is calculated, it's essential to know the key components that contribute to a node's importance score. These components include:

• Vesting: The amount of currency held by a node over time. Nodes that hold their currency for longer periods are considered more important.
• Transaction Activity: The number and value of transactions made by a node. Nodes that are actively transacting are seen as more important to the network.
• Network Connectivity: The number of connections a node has to other nodes. Nodes that are well-connected and help maintain the network's integrity are given higher importance scores.

Calculating Proof of Importance

The calculation of PoI is a complex process that involves several steps and algorithms. Here's a detailed breakdown of how it is calculated in the NEM network:

• Determine Vesting: The first step is to calculate the vesting score. This is done by assessing the amount of currency a node has held over a specific period. The longer the currency is held, the higher the vesting score.

• Assess Transaction Activity: Next, the system evaluates the node's transaction activity. This includes the number of transactions, the value of those transactions, and the frequency of transactions. Nodes that engage in more transactions, especially those of higher value, receive a higher transaction activity score.

• Evaluate Network Connectivity: The third component is the node's connectivity to other nodes. This is measured by the number of unique nodes a node has transacted with. Nodes that are well-connected and help maintain the network's integrity receive a higher connectivity score.

• Combine Scores: The final step is to combine these three scores into a single importance score. The NEM network uses a proprietary algorithm to weigh these factors and calculate the overall importance of each node.

Example of PoI Calculation

To illustrate how PoI is calculated, let's consider a hypothetical example. Suppose we have two nodes, Node A and Node B, in the NEM network.

• Node A: Holds 10,000 XEM for 6 months, makes 50 transactions per month with an average value of 100 XEM, and is connected to 20 other nodes.
• Node B: Holds 5,000 XEM for 3 months, makes 20 transactions per month with an average value of 50 XEM, and is connected to 10 other nodes.

To calculate the importance score for Node A:

• Vesting Score: High due to holding 10,000 XEM for 6 months.
• Transaction Activity Score: High due to 50 transactions per month with an average value of 100 XEM.
• Network Connectivity Score: High due to being connected to 20 other nodes.

To calculate the importance score for Node B:

• Vesting Score: Lower due to holding 5,000 XEM for 3 months.
• Transaction Activity Score: Lower due to 20 transactions per month with an average value of 50 XEM.
• Network Connectivity Score: Lower due to being connected to 10 other nodes.

After combining these scores using the NEM algorithm, Node A would have a higher importance score than Node B, making it more likely to be chosen to harvest new blocks.

Benefits of Proof of Importance

PoI offers several benefits over other consensus mechanisms:

• Encourages Active Participation: By rewarding nodes based on their activity and connectivity, PoI encourages users to engage more with the network.
• Reduces Centralization: Unlike PoS, where wealthier nodes have a higher chance of being chosen, PoI considers multiple factors, reducing the risk of centralization.
• Promotes Network Health: By rewarding nodes that contribute to the network's integrity and connectivity, PoI helps maintain a healthy and robust blockchain.

Frequently Asked Questions

Q: Can PoI be manipulated by creating fake transactions?

A: While it is theoretically possible to create fake transactions to boost a node's importance score, the NEM network has implemented several safeguards to prevent such manipulation. These include transaction verification processes and limits on the number of transactions that can be made within a certain timeframe.

Q: How often is the importance score recalculated?

A: In the NEM network, the importance score is recalculated every 24 hours. This ensures that the network remains dynamic and that nodes are continuously incentivized to contribute to the network's health.

Q: Is PoI used in any other cryptocurrencies besides NEM?

A: While PoI is most commonly associated with NEM, other cryptocurrencies have explored similar consensus mechanisms. However, NEM remains the most prominent example of a blockchain network using PoI.

Q: Can a node with a low importance score still participate in the network?

A: Yes, nodes with lower importance scores can still participate in the network and make transactions. However, they are less likely to be chosen to harvest new blocks and earn the associated rewards.