**3. Blockchain**

Blockchain is a distributed information processing technique on which different treatments and business models can be implemented. The blockchain is a large database that is distributed among various nodes that participate in the chain. This functions as an immutable logbook that contains the complete history of all transactions that have been executed on the network5. These nodes are connected in a decentralized network, without a main computer, and they are networks called P2P (network of peers, network between equals) that communicate with each other using the same language that they transmit a message, called a token. The P2P network is a computer network in which all or some aspects work without fixed clients or servers, but rather a series of nodes that behave as equals to each other. They act simultaneously as clients and servers with respect to the other nodes of the network, allowing the direct exchange of information in any format between the interconnected computers. Usually, this type of networks is implemented as overlay networks built in the application layer of public networks as in the case of the Internet. A token (symbol, signal, or token) is a representation of the information that the network contains [10]. The information travels encrypted, due to this, it is distributed without revealing its content, as the number of transactions grows, the chain of blocks grows, and each block has its own digital footprint. Its scope is immense, and Ethereum could replace basically any intermediary, substituting products and services that depend on third parties to be totally decentralized.
