Validators play a pivotal role in maintaining blockchain consensus and security. They validate new transactions and add them to the blockchain, ensuring that all copies of the distributed ledger uphold the same state. The most common types of consensus protocols using validators are [[Proof of Stake]] (PoS), Delegated Proof-of-Stake (DPoS), and [[Practical Byzantine Fault Tolerance|Byzantine Fault Tolerance (BFT) algorithms]]. Validators earn rewards for proposing new blocks and attesting to others' blocks accurately. These rewards come both from network inflation (newly issued tokens) and transaction fees. To get these rewards, validators the following key functions: 1. Proposing: Validators propose new blocks containing transactions. In [[Ethereum]]2.0's PoS system, for example, validators are randomly selected to propose new blocks ([source](https://ethereum.org/en/developers/docs/consensus-mechanisms/pos/#proposing-a-block)). 2. Voting: Validators then vote on which block should be added next to the chain. This is part of the consensus mechanism that ensures all nodes agree on the state of the blockchain. 3. Attestation: they attest or confirm that they have seen a block at a given height or slot in the chain. For security purposes, validators verify transaction details against existing records on the blockchain to prevent [[Double-spending]] or other fraudulent activities. They also ensure that only valid transactions get added to blocks. Similarly, [[Double-proposing]] refers to a situation where a validator proposes more than one block for the same slot or height in the blockchain; this is considered malicious behavior because it can lead to [[forks]] in the network and disrupt consensus. To deter such malicious behavior, core protocols may implement measures such as [[slashing]] and penalties. Slashing involves confiscating some portion of an offending validator's staked assets.