*2.1.1 What is Blockchain?*

As it is written in Ref. [3], in 2008, Blockchain was introduced as a new technology. It began as a peer-to-peer database for recording Bitcoin cryptocurrency transactions [4]. The main objective, as it is said in Ref. [5], was to reduce any intermediaries and to allow clients to access their business directly, that is why Blockchain was created as a decentralized network of peer nodes. Each entity:


The Blockchain is a distributed database or public ledger that stores a list of all digital events or transactions that have occurred and is fundamentally shared among all participants. Only if the majority of the participating parties decide, a transaction can be valid. Moreover, it is impossible to remove or change data unless with the agreement of all or the majority of the network participants, once it has been confirmed and inputted, exactly as it is said in Ref. [6],—an analogy in nontechnical terms; it is very easy for anyone to steal a cookie from a cookie jar that is kept in a hidden place than to steal from a jar that is placed in a market place, where thousands of people are keeping an eye on.
