Resolving Forks Using the Longest-Chain-Criterion

Learn how forks are used in blockchain to broadcast the candidate block to the network.

Why fork

We showed in this section that each node is working on its own candidate block. When a node finds a solution for the Proof-of-Work, it broadcasts the candidate block immediately to the network, and all nodes accept the new block immediately if it’s valid.

Now, it can happen that two competing nodes find a solution almost simultaneously, leading to the situation that not every node receives the same block first. As a result, the nodes of the network don’t have identical information, and the individual copies of the blockchain diverge, and the system ends up with a fork, as shown in this figure. The nodes have now a different view of the world state, and the network will no longer be able to maintain a unique authoritative chronology of the blocks.

Figure 1

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