## Block Finalization
Block finalization is the process of confirming that a set of blocks on a blockchain have been permanently committed and can no longer be altered. This occurs when two or more miners come to consensus about which version of the block chain is correct and then all other versions are discarded in favor of this one. The most common method for achieving block finality is proof-of-work (PoW) consensus algorithms, such as Bitcoin’s Nakamoto Consensus algorithm. In PoW systems, miners compete to solve mathematical puzzles, and whoever solves them first adds their proposed block to the chain; if enough miners decide that it’s valid, then it becomes part of the canonical version of history accepted by everyone else on the network.
Once these blocks have been finalized they cannot be changed or reversed unless an attacker has gained control over at least 51% percent hash power – making attacks like double spending very difficult in practice due to its extreme costliness compared with any potential reward from such an attack.
In some cases however – especially those involving permissioned ledgers or consortium chains – alternative methods may be used instead where multiple entities agree upon transactions via either voting mechanisms or pre-determined sets of rules known as smart contracts.
Overall, Block Finalization provides users with peace mind knowing that transactions are secure once confirmed beyond doubt within a certain number layers deep within a given blockchain’s architecture — giving assurance even against malicious actors attempting large scale reorganizations outside their own influence.
