the Bitcoin Protocol, in fact, consists of several transactions. These transactions are a set of different kinds of data, including the input and output of the transaction. The entrance is called Bitcoin addresses from which bitcoins are sent. Such coins can be spent only if there is a personal key associated with this address. The output is the addresses to which bitcoins are sent. Each transaction transfers bitcoins from one or more inputs (addresses) to one or more outputs (addresses). A transaction can have only one input and one output. But it happens rarely, as it requires you to send the amount in bitcoins (out) exactly matched the previously obtained sum (input).                                                                                     
                                                                                                                         
There are three main ways to identify a Bitcoin user.

First of all, although Bitcoin transactions are sent through randomly selected peer-to-peer nodes, this system is not immaculate. If, for example, an attacker has the ability to connect several nodes to the Bitcoin network, then the aggregate data collected by Them may be enough to determine the source of the transaction. Second, a Bitcoin address can be matched to a person's real identity if their identity is somehow used along with the Bitcoin address. This includes addresses that are used to Deposit and withdraw funds to or from a regulated exchange where cryptocurrency can be traded, or a wallet, addresses displayed publicly to collect charitable donations, or addresses that are simply used to send bitcoins to anyone (including online stores) with real personal data. But the most important thing is that all transactions in the Bitcoin network are completely transparent and can be tracked by anyone. It is full transparency that makes it possible to group several Bitcoin addresses and bind them to one user. Thus, if it is possible, using any other methods of overcoming anonymity, to bind to the real identity of a person some one address from such a group, then everyone will be tied.