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Staking

Validator​

There are three statuses of validators

  • Unbonded: The validator is not in the active set. They can not commit blocks and earn rewards. But they can receive delegations.
  • Bonded: The validator receives adequate bonded tokens to be the top params.MaxValidators. They can commit blocks, earn rewards and receive further delegations. They can be slashed because of their misbehavior.
  • Unbonding: The validator leaves the active set because of slashing or not having sufficient bonded tokens, all delegations must wait for the UnbondingTime before their tokens are moved to their accounts and validator.status is moved from unbonding to unbonded.

Delegation​

Aura holders who can not commit blocks may delegate Aura coins to validators and then receive rewards.

Share per Token = validator.TotalShares() / validator.Tokens()

Tokens per Share = validator.Tokens() / validator.TotalShares()

Redelegation​

The delegators who delegated Aura coins to validators can redelegate their assets to another validator immediately without waiting for the UnbondingTime. The delegator can redelegate from and to the same validator only up to 7 times and must wait for the UnbondingTime in order to redelegate from the “To” validator.

Undelegation​

Aura coins delegated to validators can be unbonded, but they may not be sent immediately to the delegator’s account. They must wait for the UnbondingTime. Similar to the redelegation module, the delegator can undelegated from the same validator only up to 7 times.

State transitions​

Validators​

The validators’ state can be Bonded, Unbonding, or Unbonded. They can move directly between all the states, except from Bonded to Unbonded. Unbonded and Unbonding are called NotBonded.

NotBonded to Bonded​

When a validator’s ranking in the ValidatorPowerIndex reaches the params.MaxValidators.

  • set validator.status to Bonded
  • send the validator.Tokens from the NotBondedTokens to the BondedPool ModuleAccount

Bonded to Unbonding​

When a validator begins the unbonding process:

  • send the validator.Tokens from BondedPool to the NotBondedTokens ModuleAccount
  • set validator.status to Unbonding

Unbonding to Unbonded​

A validator’s status moves from unbonding to unbonded when the ValidatorQueue object moves from bonded to unbonded.

  • set validator.status to Unbonded

Jail/ Unjail​

When the validators misbehave, they are jailed:

  • set validator.Jailed and update object
  • If jailed, delete the record from ValidatorByPowerIndex
  • If unjailed, add the record to ValidatorByPowerIndex

Delegations​

Delegate​

When a delegator delegates to a validator, both the validator and delegator object are updated:

  • determine the delegators shares based on delegated tokens and the validator’s exchange rate
  • remove tokens from the delegator’s account
  • transfer the delegation.Amount from the delegator’s account to the BondedPool or the NotBondedPool ModuleAccount depending on the validator.status

Begin Unbonding​

When a delegator undelegated a validator:

  • update or remove the delegation if there are no more shares
  • update the validator with removed the delegator’s shares and coins
  • remove the validator if it is unbonded and there are no more delegation shares

Complete Unbonding​

Delegators can not receive undelegation’s shares immediately and must wait for UnbondingTime before transferring the tokens from the NotBondedPool ModuleAccount to the delegator Account.

Begin Redelegation​

The delegator redelegates from source validator to destination validator:

  • perform an unbond delegation from the source validator to retrieve the tokens worth of the unbonded shares
  • delegate the unbonded tokens to the destination validator
  • if the sourceValidator.status is Bonded, and the destinationValidator is NotBonded, transfer the delegated tokens from the BondedPool to the NotBondedPool ModuleAccount
  • if the sourceValidator.status is NotBonded, and the destinationValidator.status is Bonded, transfer the delegated tokens from the NotBondedPool to the BondedPool ModuleAccount

When a redelegation begins until it completes, the delegator is in the state of pseudo-unbonding, and can still be slashed for infractions that occurred before the redelegation began.

Slashing​

Slash validator​

When a validator is slashed due to misbehavior:

  • the total slashAmount is calculated as the slashFactor x TokensFromConsesusPower, the total bonded tokens of the validator at the infraction time
  • the infraction occurred before the unbonding or redelegation began from the validator be slashed by the slashFactor percentage of the total bonded tokens. This causes the total supply of tokens decreases.

Slash Unbonding​

When a validator is slashed, all unbonding delegations from the validator that began after the infraction time are slashed by slashFactor. The slashed amount is calculated from the InitialBalance of the delegations and prevents a negative balance. Completed unbondings are not slashed.

Slash Redelegation​

When a validator is slashed, all redelegations from the validator that began after the infraction time are slashed by slashFactor. The slashed amount is calculated from the InitialBalance of the delegations and prevents a negative balance. Redelegations that began before the infraction time are not slashed. Mature redelegations that have completed pseudo-unbonding are not slashed.

How to calculate shares​

Each validator has a number of tokens T and a number of shares S.

T = sum of all tokens delegated to the validator + the rewards - the slashes.

Each delegator i has a number of shares S_i and delegator i delegated T x S_i/ S tokens to the validator.

When delegator j delegates T_j tokens and has S_j = S x T_j/ T shares.

The total number of tokens is now T+ T_j, and the total number of shares is S + S_j.

(S + S_j) / S = (T + T_j) / T

Parameters​

The staking module contains the following parameters:

KeyTypeValueMeaning
UnbondingTimestring (time ns)"1814400000000000"The duration time to complete unbonding and pseudo-unbonding processe
MaxValidatorsunint16"100"The maximum active validator
KeyMaxEntriesunint16"7"The maximum entries of the undelegations and redelegations from and to the same validator

For more detailed information about Staking, see here