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Blockchain & Cloud Computing · Module 6 of 10

Consensus mechanisms

How blockchain nodes agree on the truth.

📖 Key ideas

Consensus lets nodes agree which transactions are valid.
Proof of Work: miners solve puzzles (Bitcoin); energy-intensive.
Proof of Stake: validators stake coins (Ethereum since 2022).
Permissioned chains use PBFT/Raft-style consensus.
Trade-offs: security, speed, decentralisation (the blockchain trilemma).

💡 Real-life example: Consensus is a class vote on the correct answer, with rules making cheating costly.

Proof of WorkConsensus by computational puzzles

Proof of StakeConsensus by staked coins

ValidatorNode proposing/verifying blocks

Blockchain trilemmaSecurity, scalability, decentralisation trade-off