This FAQ was developed to help newcomers to the Agoric blockchain and smart contract platform understand the concept of a “validator,” which is a central component of how a chain like Agoric is secured. This article is part of a growing Getting Started series that explores the foundational concepts of the Agoric ecosystem.

What do validators do?

The simple answer is that validators are independent operators who run full nodes of a blockchain. That answer is just the tip of the iceberg and leads to more questions, such as: What is a full node? To back up a bit, blockchains are distributed networks of independent nodes. Validators are the operators running each of these independent nodes. These node operators are responsible for running the chain software, validating transactions, proposing new blocks, and ensuring the integrity and security of the network. A validator runs a full node and participates in consensus by broadcasting votes through the consensus protocol. At Agoric we use CometBFT, which was previously known as Tendermint. Validators will broadcast cryptographic signatures that are signed by the given validator’s private key. Validators also participate in governance by voting on proposals. When, for example, a software upgrade is available, the validators will vote whether they want to upgrade the software that they're running. If the validators agree to upgrade the software, they will vote yes; if they don't, they will vote no. If the vote succeeds, the validators will perform a network upgrade.

How many validators does a blockchain have?

The number of validators in a blockchain will vary by chain. It’s important to understand that the number of validators is a subset of a larger question of voting power. One important variable is the sort of chain consensus mechanism we’re talking about. In the case of Agoric, it’s what’s called a “delegated proof-of-stake” chain, in contrast with a “proof-of-work” chain. The proof-of-work approach, perhaps best known as the backbone of Bitcoin, requires participants to “mine,” meaning to solve complex puzzles. Bitcoin mining is resource-intensive and has been justly criticized on environmental grounds. The proof-of-stake approach is significantly less resource-intensive, and it is one by which validators, as described in this FAQ, participate in consensus.

The Cosmos Hub, which is the most widely known chain in the Cosmos ecosystem, has 180 active validators. The Agoric chain has 100 active validators. The key word here is “active.” There are, in fact, more than 100 validators on the Agoric chain. If one validator goes offline, then the 101st validator becomes part of the active set. Think of this rotation as a round robin. Various situations occur where a validator drops out of the active set, for example being jailed for excessive downtime. During that period of time, before they un-jail, number 101 will come into active set. Any nodes being operated that aren't in that top 100 are still part of the ongoing process of verifying the state of the chain; they're just not participating in consensus. The top 100 validators at any given time are participating in consensus and they're receiving block rewards (which is typically token inflation, but for some blockchains it'll be based on fees generated from network usage). 

How is a validator’s voting power established?

Because these are proof-of-stake validators, a validator’s voting weight is determined by the amount of staking tokens bonded to the validator. In addition to the number of tokens possessed by that validator, any user in the network can delegate their tokens to a validator, as well. With Cosmos chains, such as Agoric, validators are also dependent on external delegations. Delegations that come from other token holders in the network that either don't want to manage a node themselves, don't have the infrastructure for it, but do want to participate in the network. Such delegation increases the validator’s overall voting power. The amount of tokens delegated to a validator is referred to as the “stake weight.” Based on the resulting voting power, a validator, which is to say a node operator, will be considered in the “active set” if they have more staking power. This approach differs from Ethereum, where any number of people can bond their 32 ETH to create a validator. 

What equipment is necessary to be a validator?

Agoric has documented the recommended hardware baseline in our runbooks, providing the minimum requirements. These include not just the equipment but also the quality of your internet connection. Again, this varies by chain. For some blockchains, you could run a node on a PC at home, though it's not very secure to do so. For Agoric specifically, a node will generally run on a server in a data center. For example, you need at least 16 gigabytes of RAM. You need a good processor, as well, and a high performance SSD. The need for high-connectivity internet is why typically they're running a data center, but you can build a setup to run it at home. What some validators will do is they'll run their main node within a data center, but then they'll set up what's called “sentry nodes” in a cloud environment, and the sentry nodes protect their main node from being exposed to things like a DDoS attack.

What else is involved in setting up shop as a validator?

In order to become a validator, you need to set up your node, come up with your validator name (also called a “moniker” on-chain), provide a description, and set your commission rate. Your commission rate is the percent of the block rewards that you receive from delegations. At a high level, there are two types of nodes: full nodes keep a record of all historic activity, and pruned nodes process only block headers and a small subset of transactions. Full nodes are more resource-intensive than pruned nodes, but validators can choose to run either type of node as long as they retain sufficient history to validate new blocks. You can learn more about the different types of nodes in the Cosmos documentation.

What’s a good next step to learn more about validators?

Be sure to read the validator FAQ in the Cosmos documentation. That information is specific to Cosmos Hub, but it can be taken generally for any Cosmos chain regarding how they function and what role they play.

Learn more about Agoric network validators by reading their profiles in the community forum, or join the conversation on Discord.