Consensus

The Zilliqa 2.0 protocol is more flexible and efficient, delivering improved performance while minimising its costs and carbon footprint.

To improve transaction throughput, finality, operational costs, and energy efficiency, Zilliqa 2.0 shifts its consensus model from Proof-of-Work (PoW) to Proof-of-Stake (PoS).

Instead of being secured by a network of PoW nodes performing expensive computations on hardware that consumes vast amounts of energy, validators on Zilliqa 2.0 are PoS nodes that emerge from the existing Staked Seed Nodes (SSNs), who stake ZIL as collateral to secure the network.

Proof-of-Stake on Zilliqa 2.0

In Zilliqa 2.0, validators are selected by a PoS mechanism, with Staked Seed Nodes (SSNs) playing a much larger role in the network as mainnet validators.

In return for their role in consensus, SSNs earn rewards upon block production and attestation based on the amount of ZIL they have staked. 

Users are also able to deposit ZIL in the staking contract and delegate it to a validator, adding to the amount of ZIL staked by validator nodes and allowing users to share in the rewards earned for securing the network.

Users can claim their share of the rewards (minus the validator’s commission) immediately, but withdrawing and transferring their delegated stake to another validator are delayed by the unbonding period inherited from the previous version of Zilliqa.

Network Efficiency and Performance

The shift to PoS with Zilliqa 2.0 brings a number of efficiency and security improvements, including a reduction in the hardware costs required to operate a validator node on the network.

Under the previous PoW model, shard committees were required to be large to ensure the security of the network, slowing down consensus. 

The PoS model used by Zilliqa 2.0 allows these committees to be smaller, as the protocol’s security is now determined by the sum of the validators’ stake and not by their number, with a supermajority of two-thirds required for consensus.

By removing the need for validators to operate energy-intensive hardware at high cost, PoS also reduces the cost of processing transactions and allows for cheaper, faster transactions on Zilliqa 2.0.

Secure Consensus with Fast-HotStuff

For its consensus layer, Zilliqa 2.0 uses Pipelined Fast-HotStuff, an improved variant of Fast-HotStuff that replaces the pBFT algorithm used in the previous version of the network.

Fast-HotStuff is a refined variant of HotStuff, the first consensus protocol to achieve both linearity and responsiveness, meaning that it is able to scale more efficiently while remaining reliably fast.

The commit rule of Pipelined Fast-HotStuff leads to blocks being finalised after two consecutive blocks in the common case. With an average block time of around 2 seconds, this means it takes around 5 seconds to finalise a block using Pipelined Fast-HotStuff.

Pipelined Fast-HotStuff delivers further optimisations by unifying vote communication and improving resistance to forking attacks.

‍

Optional Proof-of-Authority for X-shards

Either PoS or Proof-of-Authority (PoA) can be used to drive the consensus of x-shards, the customisable and interconnected shard chains unique to Zilliqa 2.0.

When x-shards are created, they can be configured to use Pipelined Fast-HotStuff with either PoS or PoA. The selection of validator nodes under PoA is based on the specific criteria defined by individual x-shards, with the voting power of validators being unweighted and the supermajority defined as two-thirds of the validators.

The option to use a PoA consensus can be useful for efficient and legally compliant operations on industry- or application-specific x-shards where validators are selected as credentialled entities.

Improving Zilliqa’s Carbon Footprint

The shift to Proof-of-Stake with Zilliqa 2.0 improves the network's overall efficiency by eliminating the energy-intensive mining process and enabling token holders to be rewarded for securing the network.

This significantly reduces the platform's carbon footprint, aligning the network’s operations with its vision for global sustainability.

By embracing this change, Zilliqa demonstrates its commitment to eco-friendly blockchain development while enhancing scalability and resilience.