**1. Introduction**

In the mass consciousness, the term "blockchain" is associated with cryptocurrencies and financial mechanisms for avoiding centralized control over deposits. However, this view is too narrow. The blockchain is a technology for organizing distributed databases and transaction systems, associated with the databases, which should ensure reliable data storage and a possibility of their distributed processing [1]. The development of this technology supposes solution of many interdisciplinary problems in the field of cryptography, mathematics, Internet technologies and computer programming [2]. Blockchain, to put it simply, is a shared ledger, distributed over a special network, which fixes all transactions and guarantees correctness and safety of data.

A feature of the blockchain is that the confirmation of correctness of actions and accompanied data does not require involvement of a special third-party organization, as is the case of traditional transactions [3]. The validity of any actor, operating in the market, (trading organization or individual) is confirmed by validity of a node in the blockchain, which must be present in the network and visible throughout it.

There are several levels in the blockchain structure: data level; network level; consensus level; the level of incentives; contract level; and application level. The data level encapsulates kernel data and algorithms, associated with data encryption and timestamping. The data is an encrypted series of decimal digits that are decrypted using timestamps.

The network level includes methods of data distribution in the network and data validation. The consensus level includes methods of generating and distributing economic reasons, integrating by such way economic factors into the blockchain technology system. The level of contracts encapsulates various algorithms for concluding and implementing contracts (smart contracts). The application level includes other algorithms, that are not assigned to the listed levels, but are necessary in a particular blockchain models. The main innovations of the blockchain technology are the followings: the block structure; the use of timestamps; distributed node consensus mechanism; inclusion in the model of "economic reasons"; flexible and programmable smart contracts.

The following main areas of blockchain application can be distinguished now: financial system; insurance business; logistics; Internet of Things (IoT) [4]; public services [5]; social security; education [6]; digital copyright. We especially note that the implementation of the blockchain technology makes a powerful impact on the development of international financial and trade cooperation.

Evident nowadays leader in blockchain's applications is the financial sector. The Internet finance is moving to the forefront of the global financial system, being the driving force behind the introduction of new information technologies into the global economy. Along with the use of big data, mobile Internet, cloud computing, etc., blockchain is becoming the basis for the development of financial technologies.

Among the important areas, where the use of blockchain is becoming commonplace, one can also mention the energy industry [7] and, first of all, the energy market [8, 9]. Informatization of the energy market can give a significant synergistic effect for the development of national and global economies [10]. Blockchain creates prerequisites for the decentralization of the energy market [11], which is long overdue. The decentralization has especially advanced in the electricity market, where producers and consumers can be geographically close and do not need in a centralized intermediary [12]. This is especially true for alternative sources of energy (solar, wind, etc.), which do not have high power and stability and, correspondingly, product of which must be consumed locally [13].

The development of the blockchain will be effective only in conjunction with the development of other modern information technologies, which, on the one hand, facilitate the implementation of the blockchain, and, on the other hand, allow the effective use of the results of using the blockchain for effective decision-making and the overall development of the energy sector.
