(Nicolas Courtois) - specialist in cryptography and cryptanalysis, senior lecturer at University College London (University College London), author and co-author of more than 100 scientific papers (Hirsch index 32). His research interests are cryptanalysis (including the Soviet block cipher GOST 28147-89), post-quantum cryptography and cryptocurrencies. Since 2013, Courtois (alone and co-authored) has written six papers on the problems of bitcoin, sharply and justifiably criticizing some of the decisions of Satoshi Nakamoto and showing that bitcoin is nowhere near as decentralized and secure as it is commonly believed.

Is there something wrong with bitcoin? We believe that there is at least one property of bitcoin that is unjustified and should be changed as soon as possible. We first examined data on the bitcoin market in relation to the regular halving of the block reward approximately every four years. Bitcoin has been around for six years now, but the data accompanying the first halving of the reward was heavily skewed by the subsequent surge in network numbers and massive investment in cryptocurrencies. However, the block reward reduction algorithm is an integral part of the protocol and should not be ignored.

Artificial four-year cycle

Recall how the block reward change mechanism works. Every four years or so, the reward is halved from 50 bitcoins initially to 25 bitcoins since November 2012. A decrease to 12.5 bitcoins is expected in the summer of 2016.

The origin of this principle is unclear. It was NOT proposed in Satoshi in 2008: it only stated that "any needed rules and incentives can be enforced with this consensus mechanism". These constants are hardcoded in current version canonical bitcoin client. The values ​​of the constants are related to the limit on the total number of bitcoins, which cannot exceed 21 million. In fact, the 21 million money supply cap is enforced precisely by the block reward reduction mechanism. This kind of hard-coded arbitrary constants might seem like a bug, but for some reason it is often praised. Apparently, we are the first to criticize this aspect of bitcoin.

The fundamental drawback of the described state of affairs is a sharp change in an important economic indicator of the bitcoin ecosystem. This entails a serious revision of the motivations of miners and can lead to instability in the market. Surprisingly, the creator of bitcoin considered it optimal to reduce the block reward in rare sharp jumps. This decision has serious implications for the entire ecosystem.

Artificial cycle and built-in instability

In the current canonical implementation of the bitcoin client, mining rewards are halved at certain points in time. This is NOT offset by the growing difficulty of mining, but simply adds a sharp jump to the normally smoothly rising difficulty curve. We predict that the difficulty graph in 2016 will experience a gap for the first time: in 2012 this did not happen, since only a small amount of miners turned off their devices on November 29, the day the reward was reduced.

At one point next year, the profitability of mining will fall by half and a significant number of miners will inevitably lose interest in it. Investors may change their minds about investing in the IT industry, the profitability of which, at the whim of an unknown author of the protocol, suddenly fell by half and made many farms unprofitable due to a strange, unjustified rule that, in principle, was easy to change. They can withdraw funds from the Bitcoin economy and invest in another cryptocurrency. We expect the spike in Bitcoin mining performance to trigger massive market fluctuations that could last up to four years.

We argue that the current rule for changing block rewards has serious consequences. It creates an artificial four-year cycle throughout the Bitcoin economy, including for miners, traders, and investors. The rule creates incentives for a sharp movement of capital, creates “privileged” moments for investments that bring high returns. Miners will inevitably realize that they are producing a large number of SHA256 hashes at a loss and turn off their devices. Depending on the price of bitcoin, this can happen even earlier than the actual moment of the reward decrease.

The cyclicality of the bitcoin protocol is easy to fix. Developers may well agree and release a patch to the protocol that would smooth out the reward curve for miners. But whatever decision is made, it will have the most serious consequences and it will be extremely difficult to revise it later.

Do commissions make up for the reduction in reward?

Now bitcoin does not oblige to include a commission in transactions. The transaction size is determined by the user at the time the transaction is created. The fee serves as an additional motivation for the miner to include the transaction in the block. Maner can collect hundreds of commissions with each found block. Although fees are optional in theory, in practice, most wallets include fees in transactions by default. The user can insist on a zero commission, realizing that this will increase the confirmation time.

It would be strange to think that the size of commissions will change significantly in one day. Therefore, the income from commissions will not be a compensation for the halved reward for the block for the miners. At the moment when the profitability of mining decreases sharply, the miners will try to at least partially compensate for the losses due to commissions. This could be done by introducing certain new solutions. For example, miners could provide services to increase the anonymity of transactions by splitting transactions into many small ones and using newly generated temporary addresses. More transactions means more fees. In turn, bitcoin users are willing to pay higher fees for the anonymity of transactions. So eventually the sharp drop in miner income will be partly offset by higher fees, but this will not happen overnight. On the contrary, due to the described effects, the economic consequences of the halving of the reward will be felt for a long time, perhaps for the next four years.

Suggested improvement

We believe that the block reward should change much more often than once every 210 thousand blocks. Proceed with caution and allow sufficient time for the software to be updated. We propose to start gradually and change the algorithm, starting from block number 420000, for which the reward reduction is planned (2016). We want the new mechanism to largely inherit the properties of the old one. We are not supporters of revolution, on the contrary: we propose an evolutionary improvement that will preserve basic principles bitcoin. The only thing we want is to achieve smooth change block rewards.

Designing such a mechanism is not trivial. For example, we could propose to reduce the block reward every 2016 blocks (about two weeks), along with the change in difficulty (difficulty). For miners, this would be easy. The problem is that 210000 is not divisible by 2016, which worsens compatibility with old scheme, which provides for jumps every 210 thousand blocks. Therefore, we offer a reward reduction every 336 blocks. The greatest common divisor of 210000 and 2016 is 336; 336 = 3*2^4*7, 2016 = 6*336. It is easy for miners to maintain such cycles: changes will only occur at the boundaries of two cycles of 2016 or 210,000 blocks long. Interestingly, 210000 = 336*5^4, so the difficulty will change exactly 3 times a week, since 3*336*10 minutes = 7 days. This lends elegance to our solution.

Our new mechanism meets the following requirements:

1. The block reward decreases every 336 blocks, starting at block 420336, when it is just under 25 bitcoins.
2. We maintain a limit on the number of bitcoins in circulation (21 million).
3. At first, the reward will be greater than it would have been with the old mechanism, then it will become less.
4. We want to achieve a continuous change in the reward, starting from block 420000, expressed in a single simple formula.
5. Now the reward is halved every 210 thousand blocks.
6. After block 419999 is mined, there will be 15.75 million bitcoins in circulation.
7. From block 420,000, 5.25 million bitcoins remain to be mined. We must store the value of this parameter from block 420000 to infinity.

We offer the following mechanism that meets all requirements:

1. After block 420000, the reward is NOT halved.
2. The reward decreases in small increments every 336 blocks.
3. For blocks 0 - 209999, the reward was 50 bitcoins.
4. For blocks 210000 - 419999 the reward is 25 bitcoins.
5. For blocks with 420000, the reward will decrease according to the formula: for a block t = 336*k, the reward will be r(t) = 25.0*(625/624)^(1250-k) for all k >= 1250.
6. The reward is rounded up to the nearest Satoshi.

In the first two years after block 420000, the reward under our scheme will be higher than under the existing one, then it will become smaller. This is unavoidable if we are to maintain the 21 million bitcoin limit in circulation.

Block number	105000	210000	420000	420336	525000	630000	840000	1050000
date	January 2011	November 2012	2016	2016	2018	2020	2024	2028
old scheme	50,0	25,0	12,5	12,5	12,5	6,25	3,125	1,5625
New scheme	50,0	25,0	25,0	24,97	15,16	9,18	3,378	1,2417

Conclusion

We believe that investors in mining businesses are taking on significant risks associated with the uncertainty of the bitcoin specification and its future development. The reasons for the uncertainty are not only in the small size of the market compared to traditional finance, but also in some properties of the protocol. We believe that the four-year cycle of changing the block reward is not justified in any way and only brings harm. It discredits bitcoin as a stable store of value by causing regular periods of market volatility. This limits the distribution of bitcoin to a mass audience. We propose an improved formula for changing the block reward that corrects these shortcomings.

P.S.(from translator)

The proposed changes were not widely discussed and as of mid-2015 have not been implemented. Public attention is rather occupied by discussions about the need to increase the block size from the current value of 1 MB. On June 16, 2015, Gavin Andresen, who advocated a hard fork with blocks up to 20 MB, proposed a “compromise” algorithm for increasing the block size: according to his commit to the Bitcoin-XT alternative client repository, it is proposed to set it to 8 MB and double it every two years . If such or a similar scheme were adopted, what would be the economic effects of a rare spike in the maximum block size? Will block size fluctuations lead to instability in the market? There is no answer yet.

The price of Bitcoin may continue to fall over the next two years. This point of view also has the right to life and is already being actively discussed in the crypto community. It turns out that the reason for the prolonged bear market will be another cut in the reward for mining the Bitcoin block. Bitcoinist writes about it.

How halving affects Bitcoin

Recall that in May 2020, the third halving of the reward for the cryptocurrency block should take place. Judging by the published chart, Bitcoin will fall to $3,000 just before this event. The theory coincides with the previous cycles of the price movement of the coin.

According to trader Willy Wu, it is useless to compare today with the past.

In 2014, the crypto market was just beginning to recover from the collapse of MtGox. Let me remind you that at that time the exchange took over 90 percent of the total trading volume of the cryptocurrency. Now the situation is somewhat different.

After the bottom in 2020, Bitcoin is waiting for a new bull run, which will last until August 2023. By then, the cryptocurrency should reach at least $160,000. The total period between December 2017 and the new Bitcoin price record could be as long as 2,000 days.

As the block reward sharing event approaches, many people in the bitcoin space are worried about the potential for an increase in the price of the cryptocurrency.

One miner expressed serious concern that when block revenue drops, it could set off a chain of events that could lead to an inevitable hard fork.

He is the founder of Bitbank, a digital currency-based company in China that tops the list of the largest mining operations. BW recently joined the Bitbank group. On average, BW.com accounts account for about 10% of the total hashrate (the number of hashes a miner finds per second), an impressive feat given that it was launched two years ago.

Guo said, that he is afraid that if the price of bitcoin does not rise significantly before or immediately after it halves, too much hashrate will leave the network due to unprofitable mining, which makes it almost impossible to verify transactions.

The Bitcoin halving is an event that occurs every four years, in which the subsequent issuance of Bitcoin is halved. While introducing Bitcoin in January 2009, each block was rewarded with 50 BTC. On November 28, 2012, almost four years after the first launch of the Bitcoin blockchain, the reward was halved to 25 BTC.

Satoshi added a halving so that the code can produce new bitcoins as the network scales, but it also allows for a phased approach to the final stage of 21 million. However, the sudden drop could shock miners who are operating at low profit margins.

Guo believes that miners who use less efficient hardware will be forced to abandon the network if fees drop significantly.

Hardfork for difficulty

Miners earn by earning more income than they spend on electricity and related costs to keep the network running. Profit maximization in bitcoin mining is about how much hardware someone can spend to solve the next block.

The greater the hash power, the greater the chance that the miner will achieve a permanent positive result.

In order to solve this problem, Nakamoto included a complex equation in the code: every 2,016 blocks this code analyzes how much hash power is in the network and increases or decreases the complexity. During the past year, it has increased significantly.

Go's concern stems from the hard-coded time in which complexity is calculated. If more hash power is added tomorrow, blocks can be mined earlier, thus increasing profits for miners.

Goh also clarified that if the majority of miners are in offline, this will reduce a significant amount of overall mining power, which in turn will decrease when the next complication occurs.

This reduction can slow down the transaction time and create a major headache for people who want to propagate transactions. At worst, this situation will lead to a crisis of confidence in the digital currency and a complete sell-off. A drop in Bitcoin prices will cause most miners to shut down their hardware.

Seriousness skepticism

There are other communities that are also concerned about halving. Since this event has already happened once, without destroying the network, and they feel comfortable enough to head to the next event.

Bobby Lee, general manager BTCC, the Shanghai-based bitcoin exchange that hosts the third largest bitcoin mining pool with approximately 16% hashrate, agrees that there will be a drop in capacity, but he does not believe that this drop will be as large as Chandler Guo predicts.

“After mining, of course, the hashrate will drop a little, maybe up to 5-10%. But no more than 30%,” said Bobby Lee. “We have seen this happen in other cryptocurrencies with block splits, so when a block is halved, the hashrate really goes down. It's very much to be expected."

He went on to explain, this does not look like any kind of existential crisis for Bitcoin, comparing it to Donald Trap, a controversial American businessman who this moment trying to get to the presidency of the United States.

“For people who don't like Trump, they think this is a huge crisis. But after a few weeks, the anxiety goes away,” he explained.

“The important point is that power reduction will not compromise the security of the network and will not make it susceptible to attacks. We also firmly believe that the upcoming bounty reduction event will bode well for the industry as a whole as it will motivate Bitcoin companies to innovate,” said Valery Vavilov, CEO of BitFury.

No problem if the price goes up

Obviously, all this is not a problem if the price goes up,
then miners will be able to profit as before, even if the number of bitcoins generated by each block falls by half.

“If the price does not go up, it will cause some difficulties,” Guo said.

Using traditional economic theories, the combination of Bitcoin's price and the difficulty of mining it contributes to the return of its fortune before the block reward is reduced.

The wave of popularity of cryptocurrencies has taken the world by surprise. Completely virtual electronic money, subordinate to no one, controlled by no one, absolute freedom from banks and anonymity – this is what the future looks like.

Do not forget about the speculative attractiveness. Many fans of the new currency poured into the system a large amount of currency old, for example, dollars, so that operations with cryptocurrency have themselves become a means of earning money for many people.

However, in order to be able to buy or sell bitcoin for dollars, it is necessary that this bitcoin initially appeared somewhere. But nowhere in the world does there exist a single bitcoin central bank that issues currency and sends it into circulation.

This is the reason for the existence of cryptocurrencies. Where do units of digital currency come from?

Blockchain technology

Cryptocurrency founded on blockchain technology. Literally, it can be translated as "chain of blocks". It works quite simply. Each member of the blockchain network is connected to other members of the network, and all these members are called "peers".

Every time one participant wants to make a transaction, that participant's computing technology automatically sends information about this transaction to all other peers.

Pirates many times verify the authenticity of this transaction, and, if this transaction looks genuine, send it further down the network to other peers. As a result, a simple currency transfer made by one participant will be seen and authenticated by the entire network. That is why bitcoin is so safe and resistant to hacking and forgery - no one will hack the entire network.

Mining

But transactions don't just roam the network, being verified over and over again. Some members of the network voluntarily assume additional obligations. They collect these transactions in batches and try to pack them into a “block”. The block collects the transaction and other data about it, for example, the time at which it was made. As soon as the block is typed, the peer that collects it begins to select a code for this block.

Why pick up some more codes? The point is that transaction information protected by special digital technology still used in banking. This technology is called "secure hashing algorithm".

To put it briefly and simply, in this technology an arbitrary piece of information is provided with an individual “fingerprint”, a long code, and this piece of information can only be decrypted using this code.

For a block in the blockchain network, such a fingerprint is called "suitable hash", and if such a hash is found, the block is considered working and is sent to the network to a long chain of the same blocks with other transactions. This hash is searched for by searching for suitable options, but there are a huge number of such options. Therefore, their enumeration requires powerful computing equipment, and this process can take considerable time.

Block Reward

Once the hash is found, the block is finally packaged and sent to the network, to other participants so that they can verify its authenticity, and the joyful "parent" of the block automatically receives a reward - several units of cryptocurrency to their account. This reward is taken from a special "null" transaction that starts each block and guarantees a payout to anyone who can compute that block.

Due to the complexity and similarity with the extraction of valuable ore, this process is called mining, which means “mining, mining”. A peer that computes blocks is called a miner.

It can be said that miners are accountants. It is they who maintain the cryptocurrency infrastructure by collecting, systematizing and authenticating all transactions on the network. Since it takes a lot of computing power, and, as a result, a lot of electricity and resources computer science, miners are rewarded for their work for the benefit of the blockchain network with cryptocurrency.

That is, bitcoin is literally taken from the air, issued as a reward to those who support the system. This issuance is the only way to issue cryptocurrency into circulation.

Miners work voluntarily and by choice, so transaction processing speed may vary. To increase the speed of calculation of his own transaction, the author of the transfer can add a commission to it. This commission is paid to the miner who can calculate the block with this transaction.

The amounts of such commissions are usually small, but stable, while the block reward decreases over the years, and the complexity of calculations increases.

Beyond accountants-miners there are archivists- the so-called "full nodes" that store the calculated blocks. Unfortunately, there is no reward for simply storing transaction archives.

A reward is given for finding a block of bitcoin
In May 2017, the Bitcoin network faced a major challenge. The number of unconfirmed transactions in the mempool reached 200 thousand, and the total amount of raw data exceeded 120 MB. Considering that 1 block in the Bitcoin network is 1 MB, and the average time of its creation is about 10 minutes, the queue of 120 blocks stretched for several days, as more and more unconfirmed transactions constantly arrived.

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By increasing transfer fees, it was possible to temporarily reduce the number of pending transactions in the queue, but this measure, of course, could not be considered sustainable. And it is all the more surprising that miners from time to time find and close empty blocks, that is, instead of completely filling them up to 1 MB, or 4-5 thousand transactions, the block does not contain any information related to transactions.

At some point, the number of empty blocks reached a quarter of all blocks generated by the system, and they continued to be created even when the mempool was overloaded with tens of thousands of unconfirmed transactions.

What is a Bitcoin Mempul? Where to watch Bitcoin Mempool

According to statistics provided by Bitfury, at the end of 2015, more than two hundred empty blocks were generated monthly, by the end of 2016 their number had dropped to a few dozen. The improvements are related to the improvement of the architecture, which made it possible to increase the speed of transaction processing, however, empty blocks still continue to be created.

Bitcoin empty block statistics

What is the matter here? Let's try to figure it out.

How is a Bitcoin block created?

Each new block is an element of the blockchain chain that contains a set of records of transactions performed on the network that are new from the point of view of the previous chain. A new block is added to the end of the blockchain, it contains, among other things, information about the previous state of the chain, and no further changes to its structure are possible.

That is, a continuous chain of blocks is a kind of ledger where all the operations that have ever been performed in the system are recorded. Any user must be sure that the accounting system is not forged. How is such confidence formed?

The block structure includes a header - a personal decision for the block, and miners are engaged in its search. They take information from the block and begin to process it, making some mathematical operations to end up with a short sequence of letters and numbers that match predefined properties. This sequence is called a hash.

Miners mine bitcoins

In order for the block to get the opportunity to be recorded in the blockchain chain, it is required to find a special hash parameter, the indicator of which is lower than a predetermined value. Until the miner has found this parameter by random enumeration, the block is in operation.

How to build a mining farm, step by step instructions

If the miner finally solved the problem, then he informs the entire network about the receipt of a new block. The found block is checked by full nodes of the network, and after verification it is included in the blockchain. To “adjust” the processing speed to the growth in the power of the entire computer network, every 2016 blocks, the complexity is recalculated so that the time to search for a new block is approximately 10 minutes.

This is what creating a new block looks like. The hash of the last block found during the recalculation becomes a kind of “seal”, that is, it seals the block and confirms the validity of the entire previous chain. If someone tries to conduct a fictitious transaction by changing one of the blocks, then his hash will change, and anyone who recalculates the hash of this block will immediately detect a fake.

Now let's briefly describe the structure of the block.

The structure of the Bitcoin block

The block consists of a header and a list of operations.

The header, as we already know, contains a hash (created using the SHA-256 algorithm), it also includes the hash property of the previous block, which creates continuous continuity between network blocks, a list of hashes of operations, block size, etc.

A special place is occupied by the Bits parameter - an abbreviated version of the hash value. A block will only be added to the chain when miners pick up a hash smaller than bits.

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So, the header is unique and protects the block from forgery. The block is filled with a list of transactions, each of which shows the source and recipient of the transfer.

The recipient is identified using a public (public) key, and a new transaction is created that uses the money confirmed in one of the previous transactions. Used to verify ownership digital signature, which authenticates absolutely every operation on the network.

Of course, the structure of the network

bitcoin looks complicated, especially for a beginner, but as you dive into the essence of its work, the creative genius of its creator begins to emerge, for the first time in history, solving the problem of a security flaw. Bitcoin cannot be copied or used twice, and the probability of an attack on the network tends to zero, since the attacker must have at his disposal the power of most of the nodes of the network, which becomes extremely difficult given the decentralized nature of the network.

So, we come to the most important thing. How is the work of the miner built and what does he get paid for?

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Block size and miner reward

If the system as a whole pays to perform certain actions, then the pools will perform those actions in order to get paid. This mechanism looks like this.

The miner (mining pool) receives payment for the work done from two sources:

• Firstly, it is the reward for finding a new block, which is currently 12.5 BTC (the reward will be halved in 2020).
• Secondly, as soon as a miner finds a new block, he automatically receives a fee for all transactions that are included in this block.

In the early days of bitcoin, blocks were far from full, often containing less than 10 transactions, but as the network grew in popularity, block occupancy also began to grow, which led to an increase in the queue of pending transactions. To increase the speed of transactions, they began to apply an increased commission, which led to another problem - the inability to use bitcoin for small payments.

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Many solutions to this problem have been proposed, from increasing blocks to making protocols more high level used on top of the bitcoin protocol. Until recently, developers tended to use the modified Segregated Witness (SegWit) protocol, which was called Segwit2x. With the help of it, part of the information was supposed to be taken out of the block, that is, stored separately from the blockchain chain, and the size of the block itself should increase to 2 MB, which theoretically made it possible to significantly speed up transactions and increase anonymity.

However, the hard fork scheduled for November 16 did not take place, because after the publication of its code, the community failed to reach a consensus.

Why bitcoin cash worse than bitcoin in the long run

Where do empty blocks come from?

The miner, as the logic suggests, should strive to include the maximum number of transactions in the new block, since in this case his income grows. It is all the more surprising to see empty blocks created during mining. Where do they come from?

Suppose that the miner has found the hash of the next block, let's call it N. Then, in order not to idle power, he must immediately start searching for the N + 1 block. At the same time, the miner must pass block N to other network participants, who must download it and verify the transactions included in the block. Accordingly, the miner at this moment solves two tasks at the same time - checking the transactions of block N and searching for block N + 1.

If a miner finds block N+1 before block N is verified, does he have the right to fill it with transactions? No, it doesn't. Indeed, in these new transactions there may be those that rely on transactions included in block N, which has not yet been confirmed. Even if the mempool has accumulated a queue of a large number unconfirmed transactions that need to be included in block N + 1, the miner cannot do this until the confirmation of block N has passed. And if so, then the miner closes block N + 1 empty, it will contain only one coinbase transaction, which is generated automatically and carries information about the reward for creating a block. Receives a reward and starts searching for block N + 2.

50 BTC or more than $300,000 bitcoin transfer fee! Who is bigger?

This is where empty blocks come from - this is how the blockchain algorithm works. Empty blocks are obtained due to a mismatch in the speed of confirming blocks and searching for the next ones, so work on improving the network architecture does not stop for a moment.

Solution

So, the main problem that leads to the creation of empty blocks is the speed of information exchange. Each new block must be “presented” by the pool to other full network nodes, which, in turn, must download it to themselves, and everyone has a different download speed, and then check all transactions in this block. All these operations take time.

At the time of writing, the number of unconfirmed transactions exceeded 160 thousand, and the amount of raw data was 117 MB.

In 2018, it is planned to introduce several technological solutions at once that can unload the bitcoin network and increase the speed of transactions.

The release of Bitcoin Core 0.16 is scheduled for May, in which new format addresses from Blockstream developer Peter Will, known as bech32, which will limit errors from typos and reduce risks.

The SegWit protocol will finally be widely adopted and will reduce the cost of commissions and the time of transaction confirmation.

It is also expected to introduce (in the near future) the Lightning network protocol, which is a second-level solution that can drastically reduce the cost of transactions, and make confirmation almost instantaneous. According to the developers, these solutions can significantly improve network performance.

Lightning Network is a watershed event for Bitcoin

Another interesting solution involves the use of sidechains - alternative blockchains with coins that are tied to bitcoins. They can offer fast confirmation, the use of smart contracts, and many other conveniences. The Liquid project, developed by Blockstream, is currently in beta testing and is already being used to make instant transactions between exchanges, and a stable version 1.0 may be released this year.

In addition, several projects aimed at increasing the anonymity of translations are at the final stage:

• Schnorr's signature;
• confidential transactions;
• Rootstock is a bitcoin sidechain.

These technologies were discussed in more detail in the bitcoin review, the prospects for the Top cryptocurrency should be known by heart.

2018 can be a breakthrough year for the most important crypto coin in the world. The successful work of the community will increase the reliability, anonymity, scalability of the network and will significantly reduce the time for confirming transactions and commissions for transfers. Bitcoin will take another step towards global recognition.

Bitcoin price could double in 2018 - Wall Street analyst Tom Lee