Proof of Work - 21 Lectures Learn

Proof of Work / Mining / Nodes

Proof of Work (PoW) is the backbone of Bitcoin, ensuring network security and decentralization. This consensus mechanism relies on miners solving complex mathematical puzzles to validate transactions and add new blocks to the blockchain. Each block, connected in a chain, maintains a transparent and immutable ledger of all Bitcoin transactions. Nodes play a crucial role by validating transactions, enforcing protocol rules, and maintaining a synchronized copy of the blockchain. Together, PoW, mining, and nodes uphold the integrity and trustworthiness of the Bitcoin network.

Proof of Work: 

The Proof of Work (PoW) consensus mechanism is foundational to the Bitcoin ecosystem, ensuring network security and decentralisation. At its core, PoW is a method to achieve agreement among distributed parties in the absence of trust. In the context of bitcoin, it is used to validate transactions and create new blocks on the blockchain.

In the PoW system, bitcoin miners compete to solve a mathematical puzzle requiring computational power. This puzzle is essentially a cryptographic hash function, specifically SHA-256 in bitcoin’s case, that transforms input data into a fixed-size string of characters. The challenge for miners is to find a nonce, a variable part of the block data, that results in a hash value lower than a target set by the network, which adjusts over time.

The process of finding the correct nonce is known as mining. It involves generating numerous hash values rapidly until the correct one is found. This requires significant computational resources and electricity, hence the term “Proof of Work.” The first miner to solve the puzzle gets the right to add a new block of transactions to the blockchain and is rewarded with newly created bitcoin, issued as the block reward, and transaction fees.

PoW serves several critical functions in the Bitcoin ecosystem. It secures the network by making it computationally expensive and impractical to alter past transactions or double-spend. This ensures the integrity and chronological order of the blockchain. Moreover, PoW provides a fair and decentralised way to issue new Bitcoin and incentivises miners to maintain network operations.

However, PoW is not without criticism, particularly concerning its environmental impact due to high energy consumption. Recent studies by Daniel Batten show that the mining industry is solving this problem by relying increasingly on renewable or green energy. The latest energy mix is almost 60% and, therefore, more green than other industries. 

Despite this, it remains a pivotal part of the Bitcoin protocol, embodying the principles of security and decentralisation fundamental to the cryptocurrency’s design.

SHA-256 Algorithm:

SHA-256, which stands for Secure Hash Algorithm 256-bit, is a cryptographic hash function used in bitcoin mining. It’s a key part of the process that ensures the security and integrity of bitcoin transactions. Here’s a simplified explanation of how it works in the context of bitcoin mining:

  1. Input Data: SHA-256 processes input data, which in bitcoin mining includes transactions waiting to be added to the blockchain and the previous block’s hash and a nonce, a random number.
  2. Hashing: The SHA-256 algorithm takes this input and applies a complex series of mathematical operations. These operations are designed to be easy to perform in one direction but extremely difficult to reverse. The result is a fixed-size (256-bit) hash, which appears as a 64-character hexadecimal number.
  3. Unique Output: Each unique set of input data will produce a unique hash. A tiny change in the input data, like a single character, results in an entirely different hash.
  4. Mining Difficulty: Bitcoin miners aim to find a hash that meets a specific condition set by the network, known as the difficulty target. This usually means the hash must start with a certain number of zeroes. Finding such a hash is computationally demanding and requires a trial-and-error approach.
  5. Nonce and Proof of Work: Miners vary the nonce in the input data and repeatedly apply SHA-256 until they find a hash that meets the difficulty target. When a miner successfully finds the correct hash, it’s considered proof of work.
  6. Block Addition to the Blockchain: The miner then broadcasts this successful hash to the network. Other participants verify the hash, and upon validation, the block of transactions is added to the blockchain. The miner is rewarded with new bitcoin and transaction fees.


In the Bitcoin network, nodes are individual computers that play a vital role in maintaining the functionality and security of the network. They perform several critical tasks to ensure the smooth operation of the Bitcoin blockchain.

Firstly, nodes validate transactions. Each node independently checks the validity of every transaction by verifying that the digital signatures are correct and the sender has sufficient bitcoin. This decentralised verification process ensures that no single entity controls transaction approval, enhancing security and trust in the system.

Secondly, nodes participate in the creation of the blockchain. When a new block of transactions is proposed, nodes apply a set of rules, known as the consensus protocol, to agree on the state of the ledger. This process includes verifying that the proposed block adheres to Bitcoin’s protocol rules, such as the size of the block and the correct execution of transactions.

Thirdly, nodes store and propagate the blockchain. Every full node maintains a complete copy of the blockchain, ensuring the network’s resilience and redundancy. They constantly communicate with each other, transmitting new transactions and blocks, thus keeping the network synchronised.

Lastly, nodes enforce the rules of the Bitcoin protocol. By only accepting blocks and transactions that comply with the protocol, nodes collectively enforce a consistent understanding and execution of the rules. This prevents invalid transactions and blocks from being integrated into the blockchain.


Bitcoin mining is a critical process that keeps the network secure and functional. It’s like a giant, decentralised computer network working together to verify and record all the transactions made with bitcoin. 

Miners, who are members of this network, use powerful computers to solve mathematical puzzles. To do so, they guess a random data string with the SHA-256 algorithm and try to find the right solution, which is known to everyone involved beforehand. The correct answer changes roughly every ten minutes, and the difficulty of finding it is also being adapted. Mainly to maintain the ten-minute timeframe. These puzzles are necessary to confirm and add new transactions to the blockchain, the public ledger of all bitcoin transactions.

When a miner successfully solves a puzzle, they can add a new block of transactions to the blockchain. They receive a certain number of bitcoin as a reward for their effort and the computing power they’ve used. This process creates new bitcoin, akin to digital gold mining, and ensures that transactions are secure and immutable.

Bitcoin mining requires a lot of energy and computational power, making it a resource-intensive activity. As more bitcoins are mined and more miners join the network, these puzzles become increasingly complex, requiring even more computational power. This design helps control the creation of new bitcoins, keeping the supply limited and value stable.


Bitcoin mining, a process for validating transactions and securing the Bitcoin network, requires specialised hardware due to its computational intensity. The key hardware components include:

  1. ASIC Miners: Application-Specific Integrated Circuits (ASICs) are the most efficient hardware for bitcoin mining. Designed specifically for mining cryptocurrencies, ASICs outperform general-purpose hardware like CPUs and GPUs in speed and efficiency.
  2. High-Performance GPUs: Before ASICs, Graphics Processing Units (GPUs) were the primary hardware for mining. Some miners still use GPUs, especially in regions where ASICs are less accessible. However, the chances of finding a block with this setup are incredibly low, if not impossible.
  3. Power Supply Units (PSUs): Mining consumes substantial electricity. High-quality PSUs are essential to supply stable power and maintain efficiency.
  4. Cooling Systems: Due to the heat generated during mining, effective cooling systems, such as fans or liquid cooling, are necessary to prevent overheating and ensure hardware longevity. There is a growing trend in using oil and unique liquid cooling methods to further extend the lifespan of the miners.
  5. Mining Rigs: This is the framework that houses the miners. Rigs can range from simple setups for a few miners to large-scale operations.
  6. Networking Equipment: A reliable internet connection and networking equipment are crucial for miners to stay connected to the Bitcoin network.

As bitcoin mining has become more competitive, the importance of efficient and powerful hardware has grown. Miners seek equipment with the best performance-to-cost ratio, balancing initial investment with long-term profitability. One step in doing so is using renewable sources, often the cheapest energy source. 

Furthermore, because of the adaptability of ASICs, they can be used as a lender of last resort, especially if they’re connected to an energy grid. If the grid requires more energy, the miners can turn their machines off and help. The same applies on the other end of the spectrum, where they can actually sell unused energy and help stabilise the grid. 

Difficulty Adjustment:

The Difficulty adjustment is a key feature of the Bitcoin network, ensuring its stability and security. In simple terms, it’s like a self-regulating system that adjusts how hard it is to mine bitcoin.

Imagine bitcoin mining as a global competition where miners use powerful computers to solve mathematical puzzles. Successfully solving these puzzles validates transactions and creates new bitcoin. The difficulty of these puzzles is crucial; if they are too easy, bitcoin will be created too quickly. If they’re too hard, the opposite problem occurs, slowing down the rate of new bitcoin creation.

This is where difficulty adjustment comes in. Approximately every two weeks, or every 2016 block, the Bitcoin network automatically adjusts the puzzle difficulty. This adjustment depends on how quickly puzzles were solved in the previous period. If miners solve puzzles faster than expected, usually about every 10 minutes, the network increases the difficulty, making the puzzles harder. Conversely, if puzzles are solved too slowly, the difficulty decreases, making them easier.

This system ensures a balanced, steady flow of new bitcoin and secures the network by ensuring no single miner or group of miners can easily dominate the mining process. It’s a vital mechanism that helps maintain the decentralised and fair nature of bitcoin.

The Halving: 

The Halving is a pivotal event in the Bitcoin network that occurs approximately every four years, or precisely after 210,000 blocks have been mined. This event is significant because it reduces the miners’ reward for validating transactions and adding new blocks to the blockchain by half. Initially, when bitcoin was launched in 2009, the reward was 50 bitcoin per block.

The Halving is a core mechanism of bitcoin’s economic model, designed to introduce scarcity to the digital currency and mimic the extraction of precious resources like gold. This scarcity is essential because it limits the supply of new bitcoin, making it more scarce over time. In traditional economics, scarcity can increase value, assuming demand remains constant or increases.

Historically, Halvings have been associated with significant price increases in the months following the event. This is attributed to the reduced supply of new bitcoin entering the market, which, if demand remains steady, could drive up the price.