[Ethereum-POA] Parity aura consensus 간단 분석

POA : Parity - Aura(Authority Round)

• Define of step
• Primary Node
• Block Difficulty
• Example
• Finality
• Reference

 

Define step

step=UNIX_TIME/t, 여기서 t는 duration

 

Primary Node

index=step mod n, 여기서 n은 signer 수

 

Block Difficulty

max_value(==340282366920938463463374607431768211455) + parent_step - current_step + current_empty_steps

// in parity source
// Chain scoring: total weight is sqrt(U256::max_value())*height - step
fn calculate_score(parent_step: U256, current_step: U256, current_empty_steps: U256) -> U256 {
    U256::from(U128::max_value()) + parent_step - current_step + current_empty_steps
}

 

Example

signers = ["node0", "node1", "node2"] 이고 step duration=5 일 때 아래와 같이 계산

• block number 1
  • timestamp = 1528343110
  • step = 305668622 (== 1528343110 / 5)
  • primary node index = 2 (== 305668622 / 3)
  • => miner == node2
• block number 2
  • timestamp = 1528343145
  • step = 305668629 (== 1528343145 / 5)
  • primary node index = 0 (== 305668629 / 3)
  • => miner == node0

## Latest block number : 9
## Num : 0, Step : 0, Timestamp : 0 ===> null || dif : 0 || Primary : 0
## Num : 1, Step : 305668622, Timestamp : 1528343110 ===> node2 || timestamp / step : 5 || Primary : 2
## Num : 2, Step : 305668629, Timestamp : 1528343145 ===> node0 || timestamp / step : 5 || Primary : 0
## Num : 3, Step : 305668630, Timestamp : 1528343150 ===> node1 || timestamp / step : 5 || Primary : 1
## Num : 4, Step : 305668649, Timestamp : 1528343245 ===> node2 || timestamp / step : 5 || Primary : 2
## Num : 5, Step : 305668653, Timestamp : 1528343265 ===> node0 || timestamp / step : 5 || Primary : 0
## Num : 6, Step : 305668654, Timestamp : 1528343270 ===> node1 || timestamp / step : 5 || Primary : 1
## Num : 7, Step : 305668676, Timestamp : 1528343380 ===> node2 || timestamp / step : 5 || Primary : 2
## Num : 8, Step : 305668680, Timestamp : 1528343400 ===> node0 || timestamp / step : 5 || Primary : 0
## Num : 9, Step : 305668681, Timestamp : 1528343405 ===> node1 || timestamp / step : 5 || Primary : 1

=> chain spec에 validators의 인덱스별로 node0, node1, node2이 validators.
=> 위의 result에서 step은 Parity json result이고, Primary 값은 step % 3(노드 수)
=> 즉 step 은 timestamp / step duration(config 값) && primary는 step % n(노드 수)로 결정

 

Finality

; TODO

 

Reference

• parity aura
  https://wiki.parity.io/Pluggable-Consensus#validator-engines
  https://wiki.parity.io/Aura
• parity multi set
  https://wiki.parity.io/Validator-Set.html

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