How it works

According to Blockchain France, “blockchain is a technology for transparent and secured information storage and transmission, in an environment free of central monitoring control”. It is often compared to a great database delivering secured and unalterable data, in which all communications between members of a single blockchain are registered. Jean-Paul Delahaye, mathematician, draws parallels with “a huge notebook which anyone can read openly and for free, and in which anyone can write, but which cannot be erased or destroyed.” In addition, these databases may be public (open access) or private (restricted access to a few members).

For security purposes, this giant notebook is not stored in just one place. It is shared by all users therefore distributed onto thousands of thousands of computers (= knots), and constantly updated. Data hosted are thus easily checked, tamper-proof and indelible. Let’s take a person wishing to modify a data or hack blockchain. As there is no central version of such data since they are hosted in millions of computers, a tampered data cannot be replicated onto thousands of other records. 

Practically, blockchain works in quite a simple manner. All transactions carried out between users of a single blockchain are regrouped by “blocks”, secured via cryptography. A block is certified when validated by algorithm-driven network knots (computers linked to network). Once validated, it is added to a chain of blocks and is open to all users. For private blockchains, an unencrypt key is requested to access information.