Definition ∞ Longest Chain Security is a fundamental principle in many proof-of-work blockchains where the chain with the greatest cumulative computational effort is considered the valid and canonical history. This rule provides a clear method for network participants to agree on the correct sequence of blocks, especially after temporary forks. It ensures that honest nodes will always converge on the same ledger state. The integrity of transactions relies on this robust mechanism.
Context ∞ The efficacy of Longest Chain Security is a central tenet of Nakamoto consensus, offering resilience against certain types of attacks, provided a majority of computational power is honest. A key debate involves its susceptibility to 51% attacks, where a malicious actor could control enough hashing power to rewrite history. Future advancements in blockchain security models often seek to supplement or replace this principle with alternative finality mechanisms.
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