Hard fork and consensus network: nature and risk

Hard fork and consensus network: nature and risk

In the past few years, the term ‘consensus” understanding has let a person feel very confused. The term can refer to Nakamoto bitcoin written in the white paper on consensus mechanism, can also refer to the bitcoin network consensus principle. This confusion has led to the nature and limitations of network consensus risk generated a lot of misunderstanding — including hard bifurcation.


Nakamoto consensus mechanism


Nakamoto So in the white paper describes the use of the network nodes work to reach a consensus, or “general agreement” – decide which effective block chain accumulation work up, this chain is the authoritative chain block:


“When a node finds a workload, this block will broadcast to all nodes… Only in the block trading node is effective and this block will accept not spending… When a node to create a block, which indicates that the node accepts the block… Always will be the longest chain node as a real block chain, and to continue to expand the chain.”


Christian? Dekker (ChristianDecker) and Roger (RogerWattenhofer)? Watanghuofu describes all the consequences of the best block chain dispute caused by:


“At the end of a block chain branch will take longer than other branches, with the branches of the partition will switch to the branch. At this time, the block chain bifurcation problem will be solved, at the same time also copy and block books chain head (head) agreement. The abandoned block called solitary block (orphanblock).”


So, when the block to comply with the provisions of the bitcoin protocol, the network consensus on the composition of the best block chain, basically by processing the ability to decide. The miners to keep rational incentive solitary block economy, these blocks may not be included in the best block chain. If a miner mining these blocks, so the possibility of their future mining reward will be accepted will reduce network. In this way, the network nodes can in which strand is authoritative to reach a comprehensive agreement.


How to deal with the node protocol rule block? If a miners dug a repeat block or pay output increased block size, what will happen? Nakamoto So for answering this question is fairly clear: reject the invalid block, refused to use them.


In other words, a consensus mechanism Nakamoto explicitly reject the invalid block. To comply with the agreement any block is invalid. This block contains any invalid block chain will not be able to participate in the bitcoin network, at the same time, can not participate in the best block chain competition.


No matter what you told the miners, invalid block chain and the difficulty of computing power with the bitcoin network irrelevant. The miners in the agreement consensus rules without any power, these rules by each network node to enforce. Only the power miners have is in accordance with these rules in order to block the transaction.



The basic rules of network consensus


Listen to the recent hard bifurcation debate, it is easy to ignore the fact: a consensus from the root of approval (rootconsent). In other words, when you choose to use the bitcoin network, you are agree with the provisions of the agreement from the source network. The user through the node in node is responsible for the implementation of the consensus rule. Therefore, individual users agree is the basis of network on the implementation of the consensus rule.


This is an important philosophical meaning of hard branch. Change is not only a hard bifurcation software; it means that every user to migrate to a new network. Hard bifurcation essence is the formation of a new system with the new regulations, and the network is not fully compatible with the original. Therefore, by definition, hard bifurcation violated user agreement, which is a consensus network (bitcoin foundation).


For the bitcoin network, there is no “hard to reach a consensus for the bifurcation. Never exist in these cases. There is not a kind of mechanism to allow all bitcoin software users can agree to transfer network. Essentially, the user does not agree with the hard bifurcation — the so-called ‘agree’ exists only in hindsight, that after the occurrence of bifurcation (when some users decide to choose the new network). Do not agree with any transfer network of people would not agree to change the agreement.


In other words, before any hard forked majority in favour of “(for example, through calculating the stress distribution of currency holdings or vote) is only an inaccurate poll, cannot be replaced by selecting the network obtained by the consent of the user. Hard fork violates the basic philosophical principles of distributed consensus of the underlying network, so hard bifurcation is a real threat to the integrity of the chain block.


The network consensus vs. “social consensus.”


Bitcoin and etheric Fang hard supporters tried to seek to define “bifurcation social consensus” instead of “social consensus consensus” means if most users agree to a specific plan, even if the plan will break the consensus rule can be implemented. The underlying logic is that if most people agree with the hard bifurcation, then the existing consensus can be subverted, which occupied most of the rulers of economically forced minority to transfer the network against his will.


Overall, this underestimates the controversial hard bifurcation of the risks, because it wrongly assumes only one block chain will survive. It is worth noting that the choice was the bifurcation of the agreement did not withdraw your original agreement with individual users may through their tokens on the two chains will seek to maximize the value of the token.


In the hard after the bifurcation, the etheric Fang now recognise the user simply assume that occupy the bifurcation block chain will die a few, this assumption is very dangerous. If users continue to use the original network market show the newly created demand — the original token block chain is worth of mining. In this case, a controversial hard bifurcation will lead to the emergence of a plurality of chain blocks. As ETH/ETC demonstrates, speculators can through the establishment of demand for the original chain and further challenge hard token bifurcation, incentive block chain network to defend the original miners by splitting network.


Perhaps more importantly, this kind of management method and bitcoin (or any other similar distributed consensus network) security commitments directly contradict the basic. Even if we accept the actual argument about trading in a chain / mining will cause economic losses, it is enough to force a few people migrated to the hard bifurcation of the network, the philosophical foundation of this idea with the blockchain instead. When you choose this network, you and all the other participants will need to perform this agreement, which requires you to reject the invalid block, don’t give up the consensus rules, even if the 51% (or 75%) absenteeism tells you to do so. This attempt to undermine consensus is to participate in the network consensus idea attack. If a majority of the miners can be forced to abandon these network reached by all users, and just because it has an advantage, then Nick? Saab (NickSzabo) hard bifurcation called “technically equivalent to 51% attack” is correct.


We can learn from the TheDAO bifurcation of what?


TheDAO bifurcation is an ideal case of a controversial hard bifurcation. TheDAO is a building on the application of Ethernet protocol to raise the public square.


In June this year, unidentified attackers using TheDAO code vulnerabilities will transfer funds. This leads to the loss of investors tens of millions of ETH. A part of the etheric square community decided to implement the bifurcation hard to reverse this theft, ETH returned to the original owner.


Despite polls of the community, but most users (based on Ethernet Ethernet square currency holdings) and miners (according to the calculated stress) did not participate in the vote. But even so still a hard branch. If some users still use the original It is as expected, the chain, resulting in the two block of hard branch chain in separate and incompatible networks: Ethernet and Ethernet Fang Fang (bifurcation) (original chain).


Why TheDAO bifurcation is controversial?


The crux of the problem lies in the code that was used: the location of the application layer (not protocol layer). When the agreement has defect, all network participants will have a negative impact; therefore, all users will be motivated to fix this problem. Although unlikely to be hard to solve the defects of bifurcation of consensus, but according to rational user incentive analysis, this time will be hard to obtain a more widespread support branch.


The closest example is bitcoin occurred in 2010 the value of overflow error and subsequent soft bifurcation. Note: when the solution is soft bifurcation, break the consensus rule would not be a problem. Bitcoin has never been hard bifurcation.


Bitcoin value overflow original error (token supply accident exceeds the number of restrictions of agreement) destroyed the basic value of bitcoin Supply Co. limited premise. This Agreement caused a negative effect to all bitcoin users, diluting their share in all mining bitcoin (the overflow bitcoin supply expanded about 45000 times). After several hours of defects, the bitcoin network of illegal block implementation of the soft bifurcation, reject all output value overflow transactions, all transactions and payment of more than 21 million BTC. At the height of 74691 blocks, the soft branched chain of more than the violation of the chain, and the chain of isolated violations.


TheDAO bifurcation and obvious bitcoin is different, it is a hard to solve the defects of a bifurcation, the application layer instead of protocol layer. Because the protocol does not appear, so there is no reason to believe that this hard bifurcation will receive broad support.


However, the fund continues to describe the etheric etheric Fang Fang (bifurcation) is a “unstoppable application” platform, “written entirely in accordance with the operation, no downtime, review, possibility of fraud or third party interference. TheDAO co-founder StephanTual also claimed that the “code of law.”


Ethernet square community is based on ‘irresistible application “and” third party intervention “principle, so that the whole group of users can be motivated to bifurcation of their agreement, in order to rescue a third party applications, this assumption is not reasonable. Because TheDAO is an application, only a small number of users to participate in the TheDAO Ethernet square sale. When the TheDAO theft occurred, only a small number of users affected by the etheric fang. It is as expected, only a few ETH owners and miners support hard branch.


Although according to the distribution of miners after bifurcation, 99% miners Ethernet Fang (bifurcation), but the remaining 1% users are used to ensure adequate Ethernet (original square chain) can not change the nature and consensus. Therefore, two square blocks have the value of Ethernet chain — it is clear that for the miners, the two chains have the mining value, therefore the etheric Fang One divides into two.


Effect of bitcoin


The bitcoin means what? The answer is twofold.


First of all, bitcoin may start a hard fork is not controversial? The basic question is: remove the consensus rules generally involving security and philosophy of compromise. The block size argument as an example, one party is composed to the center of the doctrine, these people point out the necessity and the fee to the center of the market and node force is irresistible reason to enhance the throughput in the case of no expansion mechanism. The other side that maintain low fees and expand the use for all P2P to the center and security issues crucial bitcoin. When the two sides should give priority to ensuring the compatibility, how can we expect them to be able to reach hard bifurcation non controversial?


VitalikButerin pointed out that a very important point, he said thoughtfully:


“When someone tries to answer” I think A is good “and” why not do it at the same time than B, I suggest that we use the term “refuse to compromise doctrine”.”


Can you imagine 100% bitcoin people willing to sacrifice safety for a chance to expand the use of bitcoin? Any time the need for compromise, are inevitably there will be controversial.


Over the years, many bitcoin users have complained of a lack of use to promote bitcoin become the mainstream of the “APP killer”. On the contrary, bitcoin “APP killer” in the beginning of creation has been launched: go to the center of a controllable inflation on the books based on mathematics, anti censorship money. This is bitcoin is mainly used in the case; this drive bitcoin demand is the basis of bitcoin value. The controversial hard lead network split bifurcation risk is a serious threat to the use case and the idea for global books. PieterWuille said in a statement:


“No matter how you determine the handover date, do not know what time (or not) everyone changed their whole node (or other software). And even force the voting rate is very high, can not stop will occur after the bifurcation. The best case, people will not guarantee their transaction verification is meaningful (because sometimes verify obviously another person was adopted, and they need to switch). In the worst case, there will be a branch chain, two community, and you hold in the branch before coins in this time and in this two chain, you can reuse these coins, or repeat payment. This damage to the main design bitcoin purpose: to prevent duplicate payments.”


Secondly, the basic premise and the basic concept of security is hard bifurcation bitcoin attack. No software can be used to determine whether the user agrees to delete consensus rules. Bitcoin community there is a common misconception that the bifurcation can impose the hard to force. This idea wrong essence and essence of soft hard bifurcation bifurcation confusion together. EricVoskuil explained:


“Hard for bifurcation, the new deal even if did not comply with the original rules may also be effective. For soft bifurcation, the new deal only to comply with the original rules will be effective. In other words, some currency holders do not agree with the hard fork, but essentially accepted soft bifurcation… As long as the soft bifurcation has most stress conditions can be implemented. In other words, in fact, does not change the soft bifurcation between people’s consensus, a change it is only those who control most of the force is carried out by people… The first white paper does not clearly distinguish these rules, and the effect will be two situations as a consensus. However, the soft rules are called “consensus bifurcation rules” is wrong.”


So, have the most stress can through the implementation of the new rules to soft bifurcation. However, if that is what is the relationship between the force and the software consensus rules, which is not accurate. Absolutely cannot determine the user agrees to miners (e.g., consensus rules) – unless they run their own node. When some of the well-known developers, mining executives and Industry Promotion Center pool “by the miners’ vote to decide to change the idea of consensus,” this is equivalent to a direct bitcoin attack – this is your money for a direct attack. PieterWuille pointed out:


Bitcoin is not a democracy. The node security model is designed to minimize the required system of trust parties. This is in accordance with the rules by consensus as much as possible to verify the implementation of the. In particular, there is no so-called majority can override other things’ (which some people think so instead, this is not “the longest chain win, a majority of miners have decision-making power”; even with the support of most of the miners cannot steal your money or generate more than allowed subsidies, unless they convince all the other people to change their software).”


Hard fork should because of the risk and philosophical issues and objections


From the practical and philosophical point of view, obviously any attempt to split bitcoin protocol should be explicitly opposed. The bitcoin community should firmly oppose this idea — the user group (such as the mineral pool) by a vote to decide to change the rule of consensus. It is important to realize – break the consensus will threaten all weakened bitcoin can perform the basic rules of trust. If you believe the consensus rule is able to delete the democratic vote, then you will believe 21 million bitcoin supply constraints is feasible? Why? Because any future voting may eliminate the supply restrictions, as long as the majority of the dilution to early bitcoiners wealth. The only way you against this “consensus rule is theft”. Try to remove the consensus rule then opened Pandora’s box.


The reader should ask yourself: do you think the ability to change these miners should have agreed to by our users and the rules? If the answer is yes, then you have to admit that the miners quite similar to the power of the central bank. Non mining node operator and the interests of miners is not the same; non mining nodes act as a sort of miners power check. The miners refused to trust and carry out the agreement alone rule is to prevent individual miners (between miners and others) collusion against your only way. If you do not go to the center of the node verification, there is no valid distinction between miners and the central bank does not exist; they must comply with the provisions of. If you give the miners to override the consensus rules based power, then you will sacrifice safe mode of all nodes in the basic safety you — your money will no longer provide security. The use of miners as a distributed voting mechanism is very attractive, but this is and whether the user agrees with the Never mind, therefore, should Never mind and common rules.


As we discussed in the previous 2010 bitcoin value overflow event, only one case we can hard bifurcation: a negative impact on all of the user’s real flaws. Indeed, this would violate the user with hard branch. However, if we know the protocol vulnerabilities affect every user – this is the essence of protocol defects — then obviously, fix this in line with the user incentive and expectation. Any rational users will support hard bifurcation in these cases.


To be clear, unchanged and consensus in favour of the agreement limits the implementation of soft solution bifurcation does not mean that the progress and development must be stagnant. On the contrary, the block size argument, soft forking will bring incredible improvement can be extended for bandwidth and bandwidth, and not as hard as the risks caused by bifurcation. Different from just by increasing the block size to increase transaction throughput, we can optimize the transaction as the size of such a Schnorr signature mechanism greatly, in order to improve the capacity of. Once the ductility of the repair is completed in place, the door will be open to the intelligent network contract: lightning can bring no custody risk without trust contract, which will directly reduce the backbone throughput. MAST can further optimize the complex intelligent contract size. Mining pre verification (weak block) can significantly reduce the critical bandwidth, so you can quickly spread / delay and alleviate “decrease” transaction verification, to solve the problem in mining center to improve the throughput under the condition of. Improvement such as batch verification and file node can further reduce the node resources demand, alleviate the center pressure increases with the increase of the throughput.


Good expansion solution in front of us, these solutions will directly enhance the block capacity, while reducing the external effects caused by improving throughput. Why should we just break the consensus in order to improve the capacity of the block? This idea is absurd.


On the etheric Fang (the original chain) (ETC) effect


Since the implementation of the ETH developers crustily skin hard bifurcation after the etheric Fang (the original chain) appeared in the community. The consensus of integrity rules and block chain unchangeability Ethernet workshop users have started to support ETC.


Unfortunately, ETH core developers is not confined to the consequences of persist in wilfully and arbitrarily TheDAO. ETH core developers through the preparation of this “difficult bomb” effectively destroy the Ethernet protocol workshop. VitalikButerin on these effects described:


“In the 3 million 500 thousand block (one year from now), the average generation time block block 100 thousand to 25 seconds (a total of about 1 months); after more than 100 thousand blocks of time for 35 seconds (about 1.4 months); then 100 thousand block averaged about 55 seconds, a total of 2.2 months later; about 95 seconds, a total of 3.8 months, in order to block until the time of about 655 seconds, 100 thousand block of time of 26 months (Bibite currency situation slightly worse), only in the 99/2048 agreement because the downward adjustment limit after the interruption, the last block will not occur before 2021 (although the second half of 2017 the situation will become very bad).”


In fact, the block was dug out of the time interval will be more long, until the last ‘destiny’ arrival, there will be no new block was dug up. It should be noted that, in order to forcibly break the consensus and deliberate destruction of the etheric Fang protocol, showing that ETH core developers of Ethernet users incredible disdain fang. However, it is processed by the ETC problem.


Fortunately, the ETC community has the means and the moral authority to break the consensus, in order to overcome the damage. This “difficult bomb” is a kind of flaws. All users are encouraged to repair this defect, they must do so, otherwise their agreement destined to be in active, actually is no longer an active block chain.


At this time, the only way is the only way to change the hard bifurcation of the agreement is to delay the time to reply to the general level of block. We are the only opportunity to prevent hard bifurcation in controversial circumstances is limiting the consensus protocol defects change.


Many bitcoin field people have begun to support the ETC community, some people expressed a desire to bifurcation ETC agreement to limit the supply of ETC in the future and permanent inflation. This idea is wrong, this risk may fall into the controversial bifurcation in hard. Specifically, ETC inflation is a kind of safety incentive to ensure honest — it needs to remove mining safety compromise obviously, each user view are not the same. In order to prevent the network division, should focus on the adjustment of consensus change consistent with global user motivation and expectation. Any changes in a narrow range to solve the defects of the agreement may lead to controversy.


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