Double-spending

Double-spending is the unauthorized spending of the same money (either digital or conventional) more than once. As with counterfeit money, double-spending leads to supply inflation by creating a new amount of copied currency that did not previously exist. It can also devalue the currency and diminish user trust in the currency.

There are many fundamental cryptographic techniques to prevent double-spending while preserving anonymity in a transaction, including the introduction of a centralized authority (proof-of-authority) for blind signatures and, particularly in offline systems, secret splitting.. Other methods to mitigate the double-spend problem include decentralized consensus protocols such as proof-of-work and proof-of-stake.