Consensus algorithms are a critical element of any blockchain network, as they ensure the integrity and security of these decentralized systems. The first consensus algorithm developed for cryptocurrencies was Proof of Work (PoW), famously implemented by the Bitcoin network.
Blockchains are decentralized; there is no central authority, such as a bank or regulator, that verifies transactions. Instead, this responsibility is distributed across a network of computers (nodes) that verify transactions based on computer algorithms. When the nodes agree on the state of the transaction, a consensus is reached and the transaction is processed.
Consensus algorithm fundamentals
A consensus algorithm is a method by which all participants in a blockchain network synchronize to determine the current state of the distributed ledger (DLT). Through consensus algorithms, reliability is established within the blockchain network. Essentially, the consensus protocol ensures that each new transaction block added to the blockchain contains the correct information and is valid. The primary goal of a consensus algorithm is to reach a mutual agreement that is beneficial to the entire network.
The consensus mechanism is mainly used to either validate transactions and to mine tokens. Since there is no need for a third party, transactions can be made easily and securly peer-to-peer (P2P) on a decentralized basis. Security of the network is guarenteed by the algorithm which generates a hash based on the solution of a mathematical puzzle. This hash cannot be changed once created. If it would be tempered with other participants in the system would detect that something is wrong in the network. This prevents the double spending of tokens. Over time, other consensus algorithms have emerged, such as Proof of Stake (PoS) or Proof of History (PoH), which is used by the Solana blockchain.
Bitcoin's Proof-of-Work consensus algorithm
The Bitcoin consensus algorithm is the mechanism used to verify and confirm transactions on the Bitcoin blockchain. The algorithm is based on the Proof-of-Work concept, in which miners use specialized computer hardware and software to solve complex mathematical problems. These problems are so challenging that they can only be solved with enormous computing power. When a miner finds a solution to the problem, it is stored as a block on the blockchain and the miner is rewarded with a reward in the form of Bitcoin.
The PoW algorithm was used by Hal Finney in 2004 to send digital money securely and reliably without involving a third party. The first major application to successfully use this system was with the creation of the Bitcoin network in 2009. It uses the SHA-256 encryption and is now used for many other cryptocurrencies.
The Bitcoin consensus algorithm has several security features that prevent the blockchain from being tampered with. First, each block on the blockchain is processed by multiple miners simultaneously, preventing a single attack. Second, each block on the blockchain is verified by all miners to ensure that transactions are correct and there is no double spending. Third, Bitcoin's consensus algorithm is designed to make it impossible to change a block retroactively without recalculating all subsequent blocks.
