Medium of Exchange Currencies and cryptocurrencies For the DeFi ecosystem to exist, there must be a circulating medium of exchange that we define as currency in the traditional system while in the DeFi context, we call cryptocurrency. If, on the one hand, fiat money is generally under the monopolistic control of CBs, on the other, cryptocurrencies represent a form of unregulated and programmable digital money that is consensually accepted by the community members of the blockchain. New transactions are performed through the implementation of a consensus algorithm. Hence, it is on the community and algorithm that the DeFi bases its functioning.