The role of nodes in blockchain: how they ensure security and decentralization

Blockchain is not just a cloud-based database on some server. Behind its operation is a network of thousands of computers interacting as equal partners without central control. These computers have a special purpose—they are called nodes, and it is they who make cryptocurrencies secure and decentralized. But what exactly is a node? And what role do they play?

What is a node in blockchain in simple terms

At first glance, a node is just an ordinary computer. However, it is a computer with special software installed that allows it to interact with the blockchain network. When you install Bitcoin Core for Bitcoin or Geth for Ethereum, you are essentially turning your computer into a node.

Main function: a node stores a copy of the entire blockchain or part of it, verifies transactions, and relays information to other nodes. Think of it as a connection point in a vast decentralized network—that’s where the English word “node” (node) originates.

When a user sends cryptocurrency, their transaction does not go to any server. Instead, it spreads through the network of nodes, each verifying that everything is in order: whether the sender has enough funds, whether the digital signature is correct. Only if the majority of nodes agree that the transaction is valid, it will be added to the blockchain.

How a node participates in transaction verification

The process is somewhat similar to people calling a hotline to confirm news. Here’s how it works:

1. Receiving and verification – when a node receives a new transaction, it immediately checks all details. It ensures the signature is correct and that the sender is not double-spending.

2. Propagation – if the transaction passes verification, the node forwards this information to other nodes. This way, data spreads across the entire network within seconds.

3. Inclusion in a block – mining nodes select verified transactions and group them into a new block. They perform complex mathematical calculations to cryptographically “seal” this block.

4. Final validation – once the block is created, all other nodes verify its authenticity and add it to their copy of the blockchain. This synchronized check guarantees that no one can forge the transaction history.

Main types of nodes and their tasks

Not all nodes are the same. Depending on your available resources and goals, you can choose the appropriate type.

Full node – the backbone of the network

A full node is the “guardian” of the blockchain. It stores a full copy of the entire blockchain from the very first block (genesis block). For Bitcoin, this is about 500 GB of disk space as of 2024; for Ethereum, even more.

Advantages:

• Complete independence – you verify all data yourself, without trusting anyone
• Maximum privacy – all transactions are verified locally on your computer
• Network contribution – you actively promote decentralization

Disadvantages:

• Requires a powerful computer and fast internet
• Synchronization can take several days
• Continuous electricity consumption

Software: Bitcoin Core (Bitcoin), Geth or Parity (Ethereum), Solana Validator (Solana), Cardano Node (Cardano).

Light node – for smartphones and tablets

A light node (Light node) is like a “smart summary.” Instead of storing the entire blockchain, it keeps only block headers—the minimal information needed for verification.

How it works:

• Downloads only block headers (a few gigabytes instead of hundreds)
• Requests proof from full nodes that a specific transaction is included in a block
• Uses SPV (Simplified Payment Verification) technology for quick validation

Advantages:

• Runs on smartphones, tablets, and low-resource computers
• Synchronizes within minutes
• Low resource requirements

Disadvantages:

• Dependence on full nodes for some information
• Less contribution to network security

Examples: Electrum (Bitcoin), MetaMask (Ethereum), Trust Wallet (various blockchains), Atomic Wallet.

Mining node – creator of new blocks

A mining node is not just an observer; it is an active participant in creating new blocks. This node competes with other miners to solve complex mathematical puzzles to earn the right to add a new block and receive rewards.

How it works:

• Collects unverified transactions from the mempool (mempool)
• Creates a candidate for a new block
• Performs millions of attempts to find the correct solution (nonce) via brute-force
• As soon as it finds a solution, immediately announces the new block
• Receives rewards in newly minted coins plus transaction fees

Requirements:

• Specialized hardware – ASIC miners for Bitcoin, GPU for other cryptocurrencies
• High electricity consumption
• Competitive model – competing with thousands of other miners

Economics: Individual miners find it hard to compete with large pools, so many join mining pools, where rewards are shared proportionally to invested computational resources. This is less profitable but more stable.

Archival nodes and masternodes

An archival node stores not only the current state of the blockchain but also the entire history of changes—how each account looked at every block. This is valuable for analysts and developers but requires enormous disk space.

A masternode (in some networks) is a reinforced node that performs additional functions, such as enabling fast transactions or governance voting. Running a masternode often requires staking a certain amount of native cryptocurrency.

How nodes communicate with each other

Blockchain is a peer-to-peer (peer-to-peer) network. No node controls another. Instead, they communicate directly:

1. Discovery – when you start a node, it finds “seed nodes” (initial servers) to learn about other active nodes
2. Establishing connections – your node maintains several simultaneous connections with other nodes (usually 8-125 in Bitcoin)
3. Data exchange – through specialized protocols, nodes transmit transactions, blocks, and other info
4. Synchronization – new nodes download the entire blockchain history from others
5. Information propagation – when a node receives a new transaction, it instantly relays it to all its peers

This architecture makes the network resilient: even if 90% of nodes go offline, the network continues to operate.

How nodes ensure security through consensus

Consensus is a mechanism that allows thousands of nodes to agree on which version of the blockchain is correct. This is especially important when the network experiences a fork (fork).

Proof of Work – the calculation race

In Bitcoin and Litecoin, Proof of Work (PoW) is used. Nodes compete to solve cryptographic puzzles. The winner gets the right to add a new block and the reward. All other nodes quickly verify their solution.

Security relies on:

• The difficulty of solving the puzzle (requires billions of computations)
• Easy verification of the solution
• Controlling the network requires 51% of the computational power, which is economically unfeasible

Proof of Stake – money as a guarantee

Ethereum 2.0, Cardano, and others use Proof of Stake (PoS). Instead of solving puzzles, validators (special node types) “stake” their coins as collateral and gain the right to create blocks.

If a validator acts dishonestly, they lose part or all (or all) of their stake. This creates a strong economic incentive for honest behavior.

How nodes maintain network decentralization

Decentralization is the heart of blockchain. Nodes make this possible:

Distributed storage – each full node has a copy of the entire history. No one can simply delete or alter data because it is stored in thousands of places simultaneously.

Independent verification – each node verifies all transactions on its own. You don’t trust exchanges or Apple—you trust the algorithm.

Geographical distribution – nodes are spread worldwide across different countries and time zones. No government can shut down the entire network at once.

Open access – anyone can run a node without permission. This prevents network monopolization by corporations.

The more people run their nodes, the more decentralized and censorship-resistant the network becomes.

Challenges and the future of nodes

There are real issues:

• Blockchain size – Bitcoin is already over 500 GB. This discourages people from running full nodes.
• Mining centralization – a large share of Bitcoin is mined by a few big pools, threatening PoW decentralization.
• Environmental costs – PoW mining consumes enormous amounts of energy.

Projects are trying to address these:

• Developing optimizations to reduce memory requirements
• Transitioning to Proof of Stake (less energy-intensive)
• Creating rewards programs for running nodes
• Developing ASIC-resistant algorithms to promote decentralization

How to choose and run your own node

Your choice depends on your capabilities and goals:

For beginners – try a light node (MetaMask, Trust Wallet). It requires no resources.

For tech-savvy believers in the project – run a full node (Bitcoin Core, Geth). You will help the network and gain maximum privacy.

For passive income seekers – consider mining (if in PoW networks) or staking (in PoS networks).

For investors with significant capital – masternodes in some networks offer substantial rewards but require substantial initial investment.

Conclusion: the future through nodes

Nodes are not just technical details. They are the lifeblood of blockchain, enabling it to remain decentralized, secure, and censorship-resistant. Understanding how they work helps you see why blockchain is a revolutionary technology.

Every node run by an ordinary person makes the network stronger. In a world where infrastructure is concentrated in the hands of a few giants, the ability for everyone to run their own network node is true power.