Effective Share Proof
In short: Effective Share Proof , more commonly called Effective Proof-of-Stake (EPoS), is a version of the Proof of Stake consensus mechanism used by the Harmony…
Effective Share Proof, more commonly called Effective Proof-of-Stake (EPoS), is a version of the Proof of Stake consensus mechanism used by the Harmony blockchain that aims for both security and decentralization. It changes how much influence a validator gets from its stake, so that power does not concentrate in a few very large validators.
Why it matters
In plain proof of stake, a validator's voting power grows in direct proportion to the stake behind it, which can let a few large operators dominate the network. EPoS limits that effect: each elected validator's stake is counted only within a band around the median stake of the elected set, so stake above the upper limit adds no further influence. This is meant to encourage token holders to delegate to a wider range of validators and to spread control across the network. Slashing, the loss of part of a validator's stake for misbehavior such as signing conflicting blocks, keeps the security side of the design in place.
Example
Imagine two validators in the same election: one backed by a very large stake and one backed by a stake close to the median. Under plain proof of stake, the large validator would get a proportionally bigger say in consensus. Under EPoS, its counted stake is capped near the median, so its extra tokens bring no extra influence, and delegators have a reason to consider validators that are not yet at the cap.