???? ?????? ?? ??????? ?????? ?? ??? ??? ??? ??????? ????? ??? ??????????:?????? ?? ????? ? ??????????? ??? ????????????? ?????????? ??????????? ?? ???????? ??????? ???? ?????????? ??? ???? ?????????? ??? ??? ??????? ???.Cryptocurrencies usually use considered one of two mechanisms to make a program of belief and decide which transactions are valid