Consensus Protocols (optional)

Joseph Reagle

Consensus protocols

Proof of work

Work summary

  • each participant has a public-key/address; they sign their transactions with private key
  • miners create a block with:
    • group of transactions
    • a hash of the previous block
    • their block reward
    • a “nonce”
    • and a hash of the block
  • valid blocks must have a hash that begins with ~60 zeroes; millions of nonces and hashes must be tried (which is a lot of work)
  • the valid ledger/chain is the longest because it has the most work
  • a cheater who generates a fraudulent transaction needs 51% of hashing capacity to keep building on their fraudulent ledger/chain
  • reward decreases over time, 21M coins total (a3Blue1Brown 2018)

Proof of stake

Stake summary

  • validators “stake” coins for a block
  • one is chosen based on: size of stake, age of coins, randomness
    • winner validates new block
    • rewarded with transaction fee
  • validators loose their stake if error/fraudulent and blacklisted
  • validators can stop and receive its stake and fees after a period

Ethereum consensus