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DOUBLE SPENDING

In this email, Satoshi Nakamoto addresses the issue of double-spending, a potential flaw in a digital cash scheme where a single digital token can be spent more than once. This is due to the token being a digital file that can be duplicated or falsified.

Nakamoto explains that when multiple double-spent versions of the same transaction occur, only one will become valid. The receiver of a payment must wait about an hour before believing that it’s valid, as the network will resolve any possible double-spending races by then.

The email also touches on the concept of transaction confirmation times. Nakamoto argues that while Bitcoin doesn’t offer instant non-repudiation, it’s still much faster than existing systems. For instance, paper cheques can bounce up to a week or two later, and credit card transactions can be contested up to 60 to 180 days later. In contrast, Bitcoin transactions can be sufficiently irreversible in an hour or two.