What is blockchain?

   Blockchain - This is a distributed database, which any person can access. Otherwise, it is called "distributed registry technology", since there is no centralized authority or regulator that can dispose of the block at its discretion.

   What is the difference between a Blockchain and a classical database? A classical database is stored on specially designed servers, which are controlled by the organization owning this database. Blocking is not controlled by any one person or organization and its security is provided by its distributed architecture. If part of the computers on which the block system is stored will be hacked, this will not affect the operation of the entire system, which is unthinkable for a classical database.

   How does it work blockchain? Theoretically, it is possible to record any data in the blockchain - from money transactions to a complete collection of world literature. In order for the data to get into the block system, they must be verified, that is, verified for authenticity. In the case of bitcoins and money transfers, the so-called miners are engaged in this. Having checked the transaction for validity, they write it to the block, after which it remains in the locker forever, and anyone can be convinced of its authenticity. Any such transaction should receive several confirmations from independent sources before it is considered valid.

What is a cryptocurrency?

   Cryptocurrency is a digital accounting unit, accounting for which is decentralized. The operation of these systems takes place using a distributed computer network. However, information about transactions is usually not encrypted and is available in clear form. To ensure the stability of the database of the chain of transactions, cryptographic elements (digital signature based on a public key system, sequential hashing) are used.

   The key feature of the cryptocurrency is the absence of any internal or external administrator. Therefore, banks, tax, judicial and other public or private bodies can not influence the transactions of any participants in the payment system. The transfer of cryptocurrency is irreversible - no one can cancel, block, challenge or force a transaction. The technology of cryptocurrency is based on the fact that the network does not have a trusted node - one whose actions are guaranteed to be true and who can confirm the correctness of other peoples transactions. To make a decision about the reliability of transactions in conditions of disbelief, any message on the network uses the technology of constructing a chain of transaction blocks, which first appeared in the Bitcoin system. To store data, transactions are combined into blocks, from which a continuous chain is formed. Continuity is provided not so much by numbering as by including the hash of the previous block in the current block - so there is no way to change the block without changing hashes in all subsequent blocks. Only the longest chain is considered true, all hashes in which meet certain requirements, which are difficult or expensive to perform. In different cryptocurrencies, Proof-of-work, Proof-of-stake or a combination thereof are used to verify the blocks.
   As a rule, in cryptocurrencies, developers initially specify the upper limit of the total volume of emissions. However, some cryptocurrencies do not have a fixed upper limit for the total volume of emissions, and both emissions and issues are possible (by mandatory destruction of a fixed amount in each transaction).