Double Spend

A double spend is a failure in a digital cash system where the same unit of currency is spent more than once. This is the fundamental problem that blockchain technology, specifically the consensus mechanism, was designed to solve.

In a double-spend attack, an actor attempts to create two conflicting transactions that both claim the same output, aiming to have the network validate both. If successful, this would destroy the trust and value of the currency.

The network prevents this by maintaining a chronological, immutable record of all transactions, which is agreed upon by consensus. Any attempt to double-spend is rejected by the honest nodes in the network.

Preventing double-spending is the cornerstone of all decentralized financial systems.