The Proof of Work (proof of work, or PoW) is a consensus mechanism used by some blockchains, such as Bitcoin, to validate transactions, secure the network, and add new blocks to the chain.

In a PoW system, miners compete their computing power to solve complex cryptographic problems. The first to find the valid solution can add the next block to the blockchain and receives a reward in cryptocurrency (block reward) as well as transaction fees.

Main characteristics:

• High security thanks to decentralization and the difficulty of computation,

• Significant energy cost because the computing power required is intentionally high,

• Resistance to attacks: one would need to hold more than 50% of the total computing power (51% attack) to manipulate the blockchain.

Advantages:

• Very secure and proven for over ten years,

• Completely decentralized with no reliance on identified validators.

Disadvantages:

• High energy consumption,

• Need for specialized hardware (ASICs) to remain competitive,

• Less scalable for processing a large number of transactions per second.

The Proof of Work is thus the historical and most well-known method to secure blockchains, but it currently faces criticism related to its environmental impact and the search for more energy-efficient solutions like Proof of Stake (PoS).