Blockchain is a decentralized data storage technology that refers to a distributed ledger consisting of separate data blocks connected to user computers (also known as nodes). Each block encrypted with a private and public key contains a timestamp and link to a previous block in the hash tree. The blockchain decentralization lies in the fact that the information about each data block is stored on all endpoints in the network. With each transaction, the blockchain system creates a new data block in the distributed ledger. To validate a transaction, the system compares the corresponding data block information stored on all nodes in the networks thus making it impossible to modify this data. Blockchain is a technology behind smart contracts and Bitcoin.