The blockchain is a decentralised and distributed database, but it has a very big problem: the cost of storage. The blockchain must always store strictly what is necessary, not one piece of data more, not one piece of data less, since the transactions associated with safeguarding the information are highly costly, and the heavier the data, the more it costs to store it. So what is to be done with the rest of the information, if only the most essential of each element is to be stored on the bl...