Unlike the fiat money, the Bitcoin has no single issuing centre and anyone can begin to issue new coins.
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Thus, there arises an unbroken chain of blocks. This chain cannot be modified, as any modification of any element will require conversion of all of the next, but this requires huge computing power comparable to the computational power of all the computers of the world, participating in the maintenance of the Bitcoin network.
In fact, the BTC network consists of two types of devices: interconnected nodes, containing the entire blockchain from the beginning and checking new data packages before adding them to the current chain. And miners, whose main task is to generate new records based on the existing chain.
Each miner, whether it is a software or a specialized hardware device, on the basis of special algorithm (for the bitcoin it is the SHA256) calculates a code (a hash), a part of which is taken from the new transactions, a part of the hash of the previous block, and a last part is some random number chosen by the miner.
The result of this calculation is unpredictable in advance it is a number consisting of a random set of 256 zeros and ones. The purpose of the miner is to find the number, adding of which to all other known parameters of the result of a calculation will give the output that is starting with a certain number of zeros.
The more computers involved in the finding for a new block (i.e. engaged in the mining), the greater the amount of zeros should be for its finding, and the less likely to find it eventually. The difficulty of the finding the package of records is constantly selfadjusting so that the average time of the finding remained constant in the network.
The original reward for the found data package was 50 BTC. In 2012, the size of the reward decreased by half and currently amounts 25 BTC. The emission algorithm provides for reduction of the award by half every four years, so in the summer of 2016, the award will be reduced again to 12.5 BTC. In 2020 it will be reduced to 6.25 BTC and so on.
The total amount of bitcoins that will be issued will not exceed 21,000,000 BTC. This number is embedded in the initial algorithm and does not depend on the quantity of devices, which are mining the cryptocurrency.
But the earlier you start mining bitcoins, the more you can earn, as the amount of new coins decreases over time with diminishing rewards. The last block for which you can get the reward will be found in 2140, so it’s not too late to join to the producing of cryptocurrencies.