2. Robustness of bitcoins

Bitcoins do not exist physically; they only exist on the peer-to-peer network. They are the result of a consensus among users who, thanks to the information available on the network that anyone can view and check, indicate how much money is in each account. All accounts are stored in a file – called the blockchain –, which is accessible to everyone. More specifically, the blockchain contains all transactions (validated per page or "block") since Bitcoin began in 2009, from which the bitcoin content of each account can be deduced.

Only the leader of a mining pool and independent validators control the correctness of transactions and their entry into the blockchain. They must have downloaded the blockchain, of which they keep a copy. They update it every ten minutes by adding a new page (block). The other miners in a pool work simply to increase its hash computing...