A blockchain , or chain of blocks [ 1 ] , [ 2 ] , is a technology for storing and transmitting information without a control organ. Technically, it is a distributed database whose information sent by users and internal links to the database are checked and grouped at regular time intervals into blocks, thus forming a chain [ 3 ] . The whole is secured by cryptography . By extension, a blockchain is a distributed database that maintains a list of records protected against tampering. or modification by storage nodes ; it is therefore a distributed and secure register of all transactions carried out since the start of the distributed system. There is an analogy with the Internet network , because in both cases the technologies employ computer protocols linked to a decentralized infrastructure. The Internet allows data packets to be transferred from a “secure” server to remote clients (it is up to recipients to verify the integrity of the data transmitt