Proof of Work (PoW) and Proof of Stake (PoS) consensus algorithms

14 June 2023

What is the consensus algorithm?

Consensus algorithms are a set of rules and protocols that are used to ensure that all nodes in a distributed network agree on its state. 

A distributed network is a collection of nodes that work together to perform a task, such as transaction processing or data storage. Each node in the network has a copy of the data, and they need to coordinate its state to ensure reliability and security.

Proof of Work (PoW) і Proof of Stake (PoS)

What is the consensus algorithm used for?

The Byzantine Generals problem answers this question well. It is an experiment that investigates the difficulty of reaching consensus in a distributed network when some nodes are faulty or corrupt. 

In the scenario, a group of Byzantine generals plans to attack the city. To succeed, they must coordinate their attack and decide whether to attack or retreat. However, the generals are in different parts of the city and can only communicate through messengers. Some of the generals are loyal, but there are also traitors who want to undermine the success of the attack. Traitors can send false messages or alter messages sent by loyal generals.

The problem is that the generals need to agree on whether to attack or retreat, but they cannot trust the messages they receive from the other generals. The challenge is to find a way to allow the generals to agree on a plan of action, despite the presence of faulty or malicious nodes.

Consensus algorithms provide a solution to a problem by ensuring that all nodes in the network agree on a single version of the truth. To achieve this goal, consensus algorithms use a process that allows nodes to reach consensus even if some nodes are faulty or malicious.

A certain number of nodes are required to agree with the message before it is considered valid. This threshold is known as "quorum," and it ensures that a message will only be considered valid if a sufficient number of nodes agree with it. This approach makes it difficult for attackers to manipulate the state of the network, since it requires control over the majority of nodes on the network.

At the moment, the popularity of the two consensus algorithms - PoW and PoS - is about the same.

Proof of Work (PoW)

Proof of Work (PoW) consensus algorithm

Proof of Work is the most well-known algorithm used in many other cryptocurrencies, including Bitcoin. When it works, network nodes are engaged in solving a mathematical problem to validate transactions and add them to the network. PoW is a resource-intensive process, making it difficult and expensive for attackers to manipulate the data.

PoW projects:

  • Bitcoin is the world's first and most popular cryptocurrency. Miners use the power of computers, servers and other equipment to solve complex mathematical problems to validate transactions and add newly arrived blocks to the blockchain. 
  • Litecoin is a cryptocurrency similar to Bitcoin, but with some key differences. Litecoin uses the Scrypt algorithm, which was specifically designed to make mining more accessible to ordinary users
  • Bitcoin Cash is a hard fork of bitcoin that was created in 2017. The PoW used in Bitcoin Cash is the same as Bitcoin, with the same block generation time and reward structure.
  • Monero is a privacy-oriented cryptocurrency. It uses a PoW algorithm called CryptoNight. It is designed so that it does not take up much memory and is resistant to ASIC.

Proof of Stake (PoS) consensus algorithm

Instead of requiring nodes to solve a mathematical problem, Proof of Stake requires nodes to bid a certain amount of cryptocurrency to validate transactions. This approach reduces the resource intensity of PoW, but requires a significant amount of cryptocurrency to participate in the network.

Examples of projects:

  • Ethereum is the second largest cryptocurrency to make the transition from PoW to PoS. In Ethereum 2.0, validators who own a certain amount of ETH pledge their coins as collateral to participate in the network.
  • Cardano - Validators are selected based on the coins they own and their reputation in the network. The selection process is determined by a combination of random selection and reputation assessment.
  • Polkadot is a blockchain network that enables interaction between different blockchain networks. Polkadot's PoS algorithm is called "Nominated Proof of Stake," which allows token holders to nominate validators to participate in blockchain production.
  • Cosmos is a decentralized network that enables communication and interaction between different blockchain networks. Cosmos uses the PoS consensus algorithm, where validators are selected based on the number of ATOMs they own and their reputation.
Proof of Stake (PoS)

Advantages and disadvantages of Proof-of-Work

Advantages of PoW

  • PoW is considered one of the most secure consensus algorithms because it requires significant computing power to solve complex mathematical problems to validate a transaction. An attacker needs more than 51% computing power to change a transaction's history.
  • PoW enables decentralization by allowing anyone with a computer and an Internet connection to participate in the network. This means that the network is not controlled by a central authority, making it more democratic and transparent.
  • PoW incentivizes miners to maintain the network by rewarding them with new coins when they successfully confirm a block. This incentive model has proven successful in motivating miners to invest in the equipment and power needed to participate in the network.

Disadvantages of PoW

  • PoW requires a significant amount of processing power to validate transactions, resulting in high power consumption.
  • As the mining process becomes more competitive, mining pools with more processing power have a better chance of confirming a block. 
  • PoW can face scalability issues as the network grows, resulting in slower transaction times and higher fees. This is because each transaction must be validated by the processing power of the network, which becomes increasingly difficult as the network grows.
  • PoW requires specialized production equipment, which can be expensive to acquire and maintain. This can be a barrier to new miners who cannot afford to invest in the necessary equipment.

Advantages and disadvantages of PoS

Advantages of PoS

  • PoS consumes significantly less energy than PoW because it does not require miners to solve complex mathematical problems to validate transactions. Instead, validators are chosen based on the amount of cryptocurrency they own, making this consensus algorithm more energy efficient.
  • PoS enables decentralization by allowing anyone with a cryptocurrency to participate in the network. This means that the network is not controlled by a central authority, making it more democratic and transparent.

Disadvantages of PoS

  • PoS is criticized for centralizing wealth in the hands of a few people who own large amounts of cryptocurrency. This is because validators are chosen based on the amount of cryptocurrency they own. This means that those with more cryptocurrency have a better chance of being chosen as validators.
  • PoS is often criticized for having less security than PoW, because it is easier for an attacker to acquire a large amount of cryptocurrency than to gain the processing power needed to attack a PoW network. This means that the network is more vulnerable to attack by attackers.
consensus algorithm


Both PoW and PoS have their strengths and weaknesses, and their suitability depends on the specific goals and requirements of a given blockchain network. It is important for developers and stakeholders to carefully consider these factors when choosing a consensus algorithm for their projects. Furthermore, ongoing research and development in the field of consensus algorithms are likely to lead to the emergence of new approaches that address the limitations of existing solutions, promoting further innovation in the blockchain ecosystem.

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Frequently asked questions about consensus algorithms (PoW and PoS)

What are consensus algorithms?

Consensus algorithms are mechanisms that are used in distributed systems to achieve unity and consistency among the participants (nodes) of the system, despite possible failures or asynchrony in the network.

Why consensus algorithms are needed?

Consensus algorithms play a key role in ensuring data reliability and integrity in distributed systems. They help to ensure that all participants in the system agree on the state of the system.

What is the difference between PoW and PoS algorithms?

PoW (Proof of Work) requires participants in the system to perform computational work (solving cryptographic puzzles) to add a block to the chain. PoS (Proof of Stake), on the other hand, is based on the participation and staking of cryptocurrency. Participants can create blocks and verify transactions based on the amount of cryptocurrency they are staking.

What are the applications of consensus algorithms?

Consensus algorithms are used in various fields such as blockchain (to validate transactions), distributed databases, networks, cloud computing, and even in resource management systems.

What problems do consensus algorithms solve?

Consensus algorithms solve problems related to asynchrony, participant and network failures, double spending, and resilience to attackers. They ensure data security and integrity.
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