What is Validator in a POS Blockchain?

A ‘Validator’ on a Blockchain is like a banker who verifies every incoming transaction. A transaction will only be completed on the blockchain when it has been verified by the validator. Validators are assigned the duty to verify transactions to whether or not they are legal and accurate. 

Every POS blockchain network is constituted of more than a single validator based upon the system requirements. Whenever transactions are broadcasted, all network validators or some validate the transactions to be legitimate and then the validated transactions are placed into the blockchain. 

WORKING

Validators in interoperable networks, like in every other blockchain network, are responsible for maintaining system efficiency, participating in voting and form new blocks in the blockchain. Blocks are selected by the validators to be added to the chain by multi-stage voting. A validator wins the right to add a block only when their block has been voted by 2/3rd or more of all validators in case of Cosmos Network. The figure below depicts the Cosmos ecosystem. 

Fig.1. COSMOS Ecosystem

Validator’s role in the network is to run a full-node and participate in the network’s consensus by broadcasting votes. Validators get revenues for committing new blocks. In case of Cosmos Network, validator should have bonded token to be incentivised validator. They are required to participate in the system’s governance by voting for proposals. They are weighted as per their owned stakes. 

Becoming a Validator

Anyone and everyone can join a public blockchain and become a validator for the network’s consensus, while individuals need permissions in private and consortium blockchains. The most commonly trusted and implemented consensus is PoS (Proof of Stake), where it randomly selects validators for block creation and validation and ensures that validators can not predict their turn. The nodes selected as validators/ block producers show commitment and interest in advancing the blockchain that they are a part of by staking their security deposit/coins. 

The selection of validators is linear to the weight of validator’s deposit. When the network finds the selected validator as offline, it transfers the validating opportunity to the next randomly selected node unless an online validator is found to create the block. The validator only gets rewarded if their produced block is added to the chain. Every other validator whose block had not been selected loses the security deposit equal to the block reward. This ensures to resolve the “Nothing-at-stake” problem.

In order to become a validator in the network, one must send a ‘declare candidacy’ transaction with details including; 1) Validator's PubKey (account to be used for validation), 2) Name and Description (optional), 3) Initial commission rate (for block provision), 4) Max commission (maximum rate), 5) Commission change rate (maximum daily increase), 6) Minimum self-bond amount (minimum bonded atoms), 7) Initial self-bond amount (initial self-bond atoms).

When an interested candidate fulfils all these requirements and signals themselves, the top candidates (in a pre-defined number set by the system) with the most stakes are chosen as validators. If over time, any validators’ stakes fall below the top number of candidates, the validator loses its rights. The number of maximum validators will be increased over time in Cosmos network as follows:

Proposer Selection Process:

After being voted, the selected validator to propose the next block is called a ‘Proposer’. These are chosen deterministically where the chances of being chosen are equal to the stakes owned by the validator. This means that the more stakes a validator owns, the more it has chances of being selected as a proposer. 

Overall, the validators on the network will have two major responsibilities:

1. Constantly run the correct version of the software using their servers and keeping their private keys secure.
2. Keep active participation in the system’s governance by voting on every proposal.

In case, if a validator is caught being dishonest in his/her decisions, inactive or double signing, then that validator will be punished. The most common types of punishments are:

• Slashing: It is the process in which a certain percentage of the validator’s shares are wasted and his/her shares decrease. 
• Losing validating powers: In this case, validators are restricted to enjoy their allotted powers and lose certain rights like decision making.
• Losing reputation: The overall reputation of the validator in the network is damaged and his/her chances of being voted 2/3rd times are reduced. When a validator loses reputation, his/her chances of being chosen as a proposer are reduced to null. 
• Losing voting rights: Whenever a validator misbehaves the system moderators may take away their voting rights for a certain period of time or permanently based upon the severity of the misconduct. 
• Inability to propose blocks: The validator might be punished such that he/she loses the right to govern the system by voting on proposals.

1. Permanent blocking: In the worst-case scenarios where the validator may be miscommunication and be involved in fraudulent activities (double signing), the validator can be permanently blocked from accessing the network while losing all his stakes at the same time.  

RNS Solutions- A Valuable Validator

RNS Solutions Singapore is running validators for multiple blockchains. It will run a node in the Cosmos Network to ensure the system’s governance, maintaining the system’s efficiency, voting for proposals and proposing blocks in the chain.