Gasper (Casper-FFG) Algorithm | cryptocurrencies, blockchains & live prices

Gasper is the consensus protocol powering Ethereum's proof-of-stake system, combining two components: Casper the Friendly Finality Gadget (Casper-FFG) for finality and the LMD-GHOST fork-choice rule for chain selection. Validators stake 32 ETH to participate and are randomly assigned to propose blocks or attest to proposed blocks in committees. Time is divided into 12-second slots and 32-slot epochs; at each slot, one validator proposes a block while committees of validators attest to it. Casper-FFG operates as an overlay that provides finality checkpoints at epoch boundaries — when two-thirds of the total staked ETH has attested to a checkpoint, it becomes finalized and cannot be reverted without destroying at least one-third of all staked ETH.

Gasper achieves economic finality through its slashing mechanism: validators who sign contradictory attestations or propose conflicting blocks have their staked ETH partially or fully destroyed. This makes attacks extremely expensive, as reversing a finalized block would require an attacker to control and sacrifice over one-third of all staked ETH, worth billions of dollars. The protocol provides liveness guarantees under the assumption that more than two-thirds of validators are honest and online. Finality is typically reached within two epochs (approximately 12.8 minutes), though the inactivity leak mechanism ensures the chain can recover even if a large portion of validators goes offline, gradually reducing their balances until the remaining active validators constitute a two-thirds supermajority.

Gasper has been live on Ethereum since The Merge in September 2022, when Ethereum transitioned from proof-of-work to proof-of-stake. It secures the largest proof-of-stake network by value, with hundreds of thousands of active validators and tens of millions of ETH staked. The protocol was developed through years of research by Ethereum Foundation researchers including Vitalik Buterin, and has been formally analyzed in multiple academic papers. Beyond Ethereum's mainnet, Gasper's design has influenced the consensus mechanisms of numerous EVM-compatible chains and Layer 2 solutions that settle on Ethereum.