What Is Double-Spending and Why Is a 51% Attack Necessary to Execute It?
Double-spending is the act of successfully spending the same cryptocurrency twice. It is prevented by the blockchain's chronological and consensus-driven nature.
A 51% attack is necessary because it grants the attacker the power to control the transaction ordering and confirmation. The attacker can send a transaction, receive goods, and then use their majority hash power to create a longer, alternative chain that omits the initial transaction, effectively reversing it.
Glossar
Longest Chain Rule
Finality ⎊ This principle dictates that the chain with the most accumulated proof-of-work or stake represents the canonical, accepted state of the ledger.
Transaction Ordering
Sequencing ⎊ Transaction ordering within cryptocurrency, options, and derivatives markets establishes the chronological execution of trades, critical for maintaining systemic integrity and preventing manipulation.
Confirmation Count
Validation ⎊ Confirmation count, within cryptocurrency derivatives, signifies the number of blocks or instances verifying a transaction’s legitimacy on a distributed ledger, directly impacting settlement finality and counterparty risk assessment.
Majority Hash Power
Consensus ⎊ Majority hash power, within cryptocurrency networks, represents the computational resources controlling block production and transaction validation; it’s a critical determinant of network security and resistance to attacks, particularly 51% attacks where control of this power could theoretically allow transaction reversal.