What is Proof of Stake in Blockchain

Verifying transactions is a key component in cryptocurrency, vital for maintaining security, efficiency, and trust within the system. While proof of work (PoW) was the original consensus mechanism used by Bitcoin, proof of stake (PoS) has become widely used across many newer blockchain networks. PoS is used by many newer blockchain networks as an alternative consensus mechanism. This article explains what Proof of Stake is and how it works in practice.

Proof of stake is a consensus mechanism used by some blockchains to validate transactions and create new blocks. Here, members contribute seeds (or resources) to earn the right to harvest crops. In cryptocurrency, the mechanism allows blockchains to validate transactions without relying on the energy-intensive process used in Proof of Work. Instead of miners, proof of stake uses validators who commit tokens (stake) under protocol rules, and their stake can be used as an economic incentive to follow the rules. This staking process involves committing a certain amount of digital currency under protocol rules, where participants may receive rewards for validating transaction blocks.

Validator selection typically depends on stake, but the exact selection and delegation mechanics vary by network. This creates an economic incentive for validators to follow protocol rules, as penalties may apply if they do not. Validator selection is often influenced by stake size, though the exact mechanism varies by network. This can reduce energy use compared with proof of work, but trade-offs depend on the network’s design and validator distribution.

In PoS, blockchain participants are referred to as validators. Validators stake crypto under the network’s rules, and selected validators propose and attest to blocks (exact roles vary by protocol).

If a validator violates protocol rules, they can be penalised through slashing, which may reduce their staked tokens. As a result, the staking model is designed to align validator incentives with network rules. After validating a block, the validator may receive rewards, typically in the form of transaction fees or newly issued cryptocurrency, depending on the protocol.

Proof of stake does not rely on proof-of-work mining, and it typically uses far less energy than proof of work. Validators typically need to stake tokens and run validator infrastructure, and selection is generally stake-weighted. The more tokens they have "locked" in their staking wallet, the more likely they will be selected as validators. This staking method generally uses less energy than Proof of Work systems, though outcomes depend on network design.

While it's possible for anyone staking crypto to be chosen as a validator, the chances are significantly lower if they only stake a small amount. During Ethereum’s transition to proof of stake, solo validation required staking 32 ETH, which led many users to use staking services or delegation-style options where available. Staking pools and services have different risk and custody trade-offs.

Proof of Stake and Proof of Work consensus mechanisms have similar goals, such as validating transactions. However, the way they ensure transactions are verified and added to the network varies significantly.

Used by Bitcoin (and previously Ethereum before The Merge), proof of work relies on miners using computational work to secure the network. This process is energy-intensive and has been criticized for its environmental impact. Proof of work and proof of stake have different security models, and security depends on specific network design, decentralisation, and economic incentives.

Conversely, PoS is a more energy-efficient way of launching and sustaining a network since it doesn't require high-powered computing; instead, it selects validators based on their staked crypto. This approach differs in how validators are selected and how transactions are processed. Ethereum is now fully PoS, and many newer cryptocurrencies use PoS for its lower environmental impact and ease of participation. 

Bitcoin and the early days of cryptocurrencies began with Proof of Work (PoW), the only way to validate transactions. The first instance of proof of stake in blockchain was Peercoin, which introduced its PoS mechanism in 2012. However, it wasn't until early Gen 2.0 protocols implemented PoS to help scale transactions and support smart contracts.

Today, many newer networks use proof of stake or PoS-like designs, often to reduce energy use and support different scaling approaches. Numerous cryptocurrencies have adopted PoS, including Ethereum, which we will discuss later, using this consensus model as part of its network design. Notable examples include Cardano and Polkadot. Cardano uses a proof of stake protocol called Ouroboros, which is designed to support security and energy efficiency.

Many newer tokens and blockchain protocols use Proof of Stake or similar consensus designs.

Since there's no bulletproof protocol immune to attacks, Proof of Stake has different security characteristics compared to other consensus mechanisms. Its reliance on financial incentives encourages validators to act honestly, as they risk losing their locked tokens for malicious behavior. Decentralization can reduce the likelihood of a single entity gaining control, though outcomes depend on network structure.

Proof of stake is not without vulnerabilities, and one possible threat is a 51% attack, which can also apply to proof of work networks. In such a case, an entity controls over half of the network's stake assets and manipulates transactions to validate others. Such attacks can be costly and complex to execute, particularly in larger and more distributed networks. 

A 51% attack generally refers to an attacker gaining majority control over a network’s consensus power, which could enable transaction censorship or double-spend attempts depending on the protocol. This type of attack poses a significant threat to any blockchain. However, for 51% to take place, a large number of tokens are required to cover over 51% of staked tokens in circulation. 

In a PoS network, the financial requirements for executing a 51% attack are typically higher than in a PoW system. This is because acquiring more than half of the network's staked coins requires substantial investment, making it impractical for most would-be attackers. 
Even so, the risk of a 51% attack serves as a reminder of the importance of decentralization and the ongoing need for improvements in blockchain security. 

Pros 

• Energy-Efficient: Unlike Proof of Work, PoS doesn't rely on high-powered machines to solve complex math problems, drastically reducing energy consumption compared to networks like Bitcoin. 
• Lower Barriers to Entry: PoS allows anyone with a wallet and some tokens to participate, eliminating the need for costly hardware and making the network more accessible. 
• Enhanced Scalability: PoS can handle a larger number of transactions, providing a pathway to greater scalability and allowing blockchains to grow without compromising speed or efficiency. 

Cons 

• Potential for Centralization: Validators with substantial stakes may gain disproportionate influence, concentrating power in fewer hands. 
• Risk of Slashing: Validators who validate incorrect or fraudulent data risk losing part or all of their staked cryptocurrency, potentially leading to a significant financial penalty. 

Ethereum's transition to PoS, known as ETH 2.0, represents a significant milestone for the blockchain industry. By replacing PoW with PoS, Ethereum aimed to improve scalability, security, and sustainability.

In Ethereum, running an independent validator requires staking 32 ETH, and validators are selected under protocol rules to propose and attest to blocks. As a result, Ethereum sought to ensure decentralization and fairness by rewarding users for their efforts and ensuring the blockchain remains relevant to the industry.

Ethereum’s scaling roadmap has evolved over time and has focused on rollups and data-availability upgrades. Some early plans discussed sharding, but current approaches differ from the original “ETH 2.0” framing. This innovative approach allows Ethereum to increase its capacity to process various transactions without endangering the network's security. 

Proof of stake has become widely used in crypto networks, alongside proof of work and other consensus designs. Proof of stake and proof of work have different trade-offs, and the “best” choice depends on network goals and design. As with any protocol, new users aren't preoccupied with how transactions are verified but rather with how quick and secure the network is. 

Further Readings

• Similarities & Differences between the Proof of Stake Implementations
• Proof of Stake (POS) vs Proof of Work (POW)
• Ethereum Transition: Impact and Significance