transmission connections with the Baltic and Nordic countries and Poland ensure the security of supply, reducing dependence on a single supplier or limited number of suppliers. The EU measures on the storage of liquid fuel supply the stability of the liquid fuel market is ensured. Estonia aims to produce power and thermal energy from renewable energy sources. In producing thermal energy, a better balance must be found in relation to the energy sources currently used, and conditions must be created so that large heat producers can switch from natural gas to other fuels. Required security and safety measures must be applied in ensuring the continuous operation of energy systems and protecting energy infrastructure. Electronic communication and transport infrastructure and their development strengthens the economy and make it more resilient. They are also directly connected to national security and therefore the economic and social development, as well as national defence requirements are taken into account in their planning and development. Organisational, IT and physical security and safety measures are applied in protecting information systems that support the functioning of electronic communications. State should constantly have an overview of the technical working condition of means of communication, communication systems and their infrastructure, and the options for duplicating and ensuring the safe functioning of these systems in times of crisis. Estonia must develop and put to use alternative solutions for making communication services available to institutions important to the functioning of the state in situations where services provided by commercial operators are down. International cooperation is necessary for ensuring cross-border communication. In this way, the interoperability of electronic communication networks can be maintained and the use of resources coordinated. In the case of transport infrastructure, it is crucially important to reconstruct or build ports and airports as well as railways and highways that form part of the trans-European transport network. From the point of view of a Host Nations Support system, the transport network plays an important role in national defence. In ensuring the continuous operation of the transport system and defending it, security and safety requirements conforming to international standards are applied. 3.6. Cyber Security The population expects that the state functions expediently and safely. Modern information technology plays an increasingly significant role in fulfilling their expectations, and employing it comes with an ever-greater responsibility. The cyber world is present in all spheres of life, inter alia, in security, so given the Estonian digital lifestyle and society’s trust in digital services the state must guarantee information integrity.7 Estonia organises cyber security uniformly using the same structural solutions during peacetime and war. Cyber defence as part of national defence system is organised in cooperation between agencies and is regularly practised. Estonia also applies measures to ensure the digital continuity of the state in a situation where it has lost control over its territory. 7 Information integrity—Data is accurate, complete, consistent and reasonable (in terms of value), and conforms with the intentions of the person who created it; in the narrow sense, no unauthorised changes have been made to the data (including that the data is identical for the sender and receiver and has been synchronised in a database). 16