How Bitcoin Reaches Consensus
📖 6 min read
Quick Answer
Thousands of strangers who do not trust each other somehow agree on a single, shared truth about who owns what — with no referee. The mechanism that makes this possible is called Nakamoto consensus, and it is Bitcoin’s real breakthrough.
💡 Think of it as…
Dav, kde každý nezávisle souhlasí, že bude následovat nejdelší a nejtěžší postavenou zeď z cihel. Pokud dva lidé založí nové zdi najednou, dav čeká a couvá podle toho, která zeď roste nejrychleji – a na opuštěnou se jednoduše zapomene.
The longest-chain rule
When miners find blocks at nearly the same time, the chain can briefly split. Nodes resolve this by always following the chain with the most accumulated proof-of-work (the "heaviest" chain). The other branch is orphaned.
Why honesty pays
Těžaři by se mohli pokusit podvádět, ale stálo by to obrovskou elektřinu a pravděpodobně by přišli o odměnu, když síť odmítne jejich blok. Pobídky jsou navrženy tak, aby dodržování pravidel bylo výnosnější než jejich napadání.
The 51% attack
If a single party controlled more than half the network’s mining power, they could in theory reorder recent transactions. For Bitcoin this would cost billions and the attacker would destroy the value of the very thing they attacked — a powerful deterrent.
🔑 Key takeaway
Consensus = follow the chain with the most proof-of-work. Cheating is possible in theory but ruinously expensive and self-defeating in practice.
Why this matters for you
This is why you can accept Bitcoin from someone in another country and trust it without a bank confirming it. Consensus is the invisible trust layer behind every cross-border payment and remittance.
Často kladené otázky
How many confirmations are safe?▼
Each new block on top of your transaction is a "confirmation". For everyday amounts 1–3 is plenty; for very large sums many people wait for 6, which makes reversal effectively impossible.
What is "finality" in Bitcoin?▼
Bitcoin has probabilistic finality — the deeper a transaction is buried, the more irreversible it becomes. After a handful of blocks, reversing it is practically impossible.
Has Bitcoin ever been 51%-attacked?▼
No. Bitcoin’s mining power is so large and distributed that a sustained 51% attack has never been economically feasible.