$BTC One of the main features of the system is full decentralization: there is no central administrator or any equivalent. A necessary and sufficient element of this payment system is the basic client program (it has open source). The client programs running on multiple computers connect to each other in a peer-to-peer network, each node of which is equal and self-sufficient. One of the consequences of decentralization is the potential for 'double spending', that is, the transfer of the same bitcoins to different recipients. Under normal conditions, the inclusion of a transaction in the blockchain protects against this. However, if one controls more than 50% of the total computing power of the bitcoin network, there exists a theoretical possibility to 'replace' one chain of transactions with another.