Introduction to consensus in blockchain

In simple terms, consensus is the process by which all participants (nodes) in a blockchain network agree on the validity of transactions and the current state of the ledger.

Since blockchain is decentralized (no single authority like a bank to approve transactions), the network needs a reliable way for everyone to trust that:

• Transactions are valid (no double spending).
• The order of transactions is agreed upon.
• The data on the blockchain cannot be tampered with.

This agreement is achieved through consensus mechanisms — protocols that ensure all nodes stay synchronized and honest.

Real-World Analogy

Imagine 10 friends are playing a group game where everyone records the scores:

• If one friend writes down a wrong score, the group needs a way to agree on the correct score so the game is fair.
• Consensus ensures that, despite mistakes or even dishonest players, the majority agrees on the right outcome.