Ethereum solves Byzantine hard bifurcation
"decentralization" is translated from the English word decentralization, which is composed of the prefix de -, stem central and suffix ization. Among them, the stem central means "center", the suffix - ization means "... Hua", and the prefix de - has the meanings of leaving, removing, canceling and opposite. Therefore, it is very accurate to translate it into decentralization
what is the meaning of decentralization
vitalik buterin, founder of Ethereum, published the article "the meaning of decentralization" in February 2017, elaborating the meaning of decentralization. He thinks that we should distinguish the centralization and decentralization of computer software from three perspectives: architecture, governance and logic
Architecture centralization refers to the number of nodes that the system can tolerate and continue to run; Governance centralization refers to how many indivials and organizations are needed to control the system; Logic centralization refers to whether the interface and data presented by the system are like a single whole
blockchain is a unified account book of the whole network, so it is logically centralized, which is beyond doubt. From the perspective of architecture, blockchain is based on peer-to-peer network, so it is decentralized. From the perspective of governance, blockchain makes it difficult for a few people to control the whole system through consensus algorithm, so it is decentralized. The decentralization of architecture and governance brings three benefits to blockchain: fault tolerance, anti attack and anti collusion
five differences between blockchain and traditional distributed system
as a new kind of distributed system, blockchain is often mistakenly regarded as a distributed database or log system. In fact, there is a fundamental difference between blockchain and traditional distributed system, namely decentralization. Now let's look at the main differences between blockchain and traditional distributed systems:
(1) consistency algorithm: what blockchain needs to solve is the Byzantine general problem, that is, there are one or more fraulent nodes in the network, which may deliberately violate the protocol or transmit wrong data, Therefore, Byzantine fault-tolerant consensus algorithms, such as BFT, pow, POS, are often used in blockchain; The traditional distributed system only needs to consider the node failure and communication errors, and often uses consistency algorithms such as Paxos and raft, which can not resist the fraulent nodes
(2) central controller: there is no central controller in the blockchain network, and no node can control or coordinate the generation of ledger data. All nodes coordinate through consensus algorithm to generate consistent ledger. However, the traditional publishing system is often controlled by one organization, which uniformly dispatches all nodes to participate in the calculation
(3) rule making: the rule of blockchain is consensus protocol, also known as consensus mechanism, and consensus algorithm is a part of it. Consensus mechanism is generally designed and developed by a person or a team, and the corresponding proceres are developed for the community to use. This seems to be the same as the traditional distributed system, but the change and upgrading of the consensus mechanism of the blockchain requires the community to have a consensus on it. If no consensus can be reached, anyone can implement hard bifurcation and build another community and chain. This is the decentralization process of consensus mechanism.
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abey blockchain technology is from Ciprian pungela & amp; Co., two doctors in the Department of artificial intelligence from the Department of computer science, School of mathematics and information, Western University of timishwara, Romania; Vorel negru's own research project. Constant lightweight blockchain technology and multi-layer programming and extended blockchain solution are adopted. The scale of abey's blockchain remains unchanged, with only 50 active blocks. Abey blockchain technology is suitable for the use of e-money in e-commerce system for mass transactions, and has multi-level, scalability and security, and can be programmed
according to the official white paper, abey is suitable for the blockchain solution in e-commerce system, which uses digital currency to carry out mass transactions and can carry out multi-layer programming and expansion
specific implementation method of abey blockchain Technology:
using a multi-level and programmable blockchain method to realize digital currency (for simplicity, we call it "DC"). This method can pave the way for the implementation of various e-commerce purposes, such as loan financing, completion of refundable transactions and non refundable transactions. In the first layer of the blockchain, we can realize the inherent digital currency design, which is commonly referred to as the base layer ("FL"). The various upper layers built on this foundation can be used to describe various additional functions related to various business driven application examples (which we will briefly introce below). All of the above levels are fully programmable, and can be easily adapted for various applications
although most of today's digital goods store transaction balance in the blockchain, abey's method is more similar to Pascal coin digital currency. This method uses what we call a "vault" encryption structure“ The "vault" structure can only save the balance of all accounts in the network, instead of a complete list of all completed transactions, and can be reconstructed in the evolution history of the blockchain. Since vault allows the deletion of useless content at any time, it can significantly rece the storage cost of blockchain. In contrast, at the time of writing this article, the storage space required to download bitcoin database is 70gb (the alarm rate is still growing, and it is expected to reach 300gb in 2019), so it is not feasible to use ultrabooks or notebooks with small storage space (such as 120GB or 256gb) to carry out mining operation. On the other hand, the size of the abey blockchain will remain unchanged, with only 50 blocks (at the time of writing, there are more than 525000 blocks in the bitcoin blockchain)
vault fully supports digital currency transfer between accounts. In addition, vault can assign an owner defined name to each account instead of using hashing algorithms like today's cryptocurrency - which makes the account easier to remember and makes the name public
one of the important functions that vault can help prevent the daily expenses of blockchain from being too high (especially those related to transaction history) is that vault can save such states and rece the size of blockchain itself by creating a secure of blockchain states. Because there is no transaction history and all accounts can save their direct balance, the blockchain information has the feature of partial erasure. All the blockchain states that can be stored can be regarded as landmarks of the blockchain
secure data sharing:
through the block chain structure design, for each transaction sent to the network, the block chain may contain encrypted metadata. The metadata can only be decrypted by the transaction recipient. For the transaction sent to the network, the sender's public key is included in the transaction, and the transaction receiver decrypts the metadata using the public key. Since the transaction receiver holds the private key for decryption, only the transaction receiver can implement the data decryption process. From the perspective of encryption method, although bitcoin is limited to elliptic curve cryptography, blockchain metadata can use any other encryption mechanism to complete the encryption process. This not only provides complete flexibility in security selection, but also does not have any adverse impact on the structure or function of the blockchain
scalability:
since the abey blockchain supports the creation of historical landmarks by design, it is very easy for the network itself to achieve high scalability from the point of view that the blockchain will always need to store (related to the latest existing SLS). This method completely eliminates the need to store transaction history to calculate the balance of all accounts, and can directly store all account balances, so as to ensure that the specific balance information provided by all nodes in the network meets the requirements of Byzantine consistency
proof of security and workload:
it is impossible to have two-way payment operation in abey's method (in the specified appropriate scenario, the vast majority of today's mainstream cryptocurrencies may theoretically have two-way payment operation). Each transaction means that the balance of the corresponding account is updated in a relatively simple way, and there is no special way to restore the transaction from the network pending transaction team. For the abey blockchain, since all technical / functional layers are built on vault, vault is the infrastructure of our blockchain, so vault is very important for mining operations. Our proposed blockchain model is composed of a series of blocks, each of which is generated by the nodes in the network who are willing to mine. All nodes in the network can update the account balance independently according to the transaction (part of the block), and are independent of other nodes. The mining operation will affect the first functional layer. In addition to updating the balance, each node can also update other matters that may belong to the upper functional layer in the composition of the blockchain structure. Once an update occurs, a new mining incentive block will be created. The mining reward block contains a number of new reward accounts that have been assigned to miners. The miner is the winner of the above reward according to the workload Certificate (currently there are 50 reward accounts). The way to reward is to distribute the public key of all such accounts to the reward recipient
blockchain technology layer:
abey's digital currency model contains a multi-layer structure, in which the first layer represents the realization of the digital currency itself (see Figure 7 for graphic explanation). The corresponding levels include:
tier 1 → digital currency (cryptocurrency): currency transfer, mining
tier 2 → refundable transaction and non refundable transaction: allowing the use of digital justice system to complete refundable transaction
Tier 3 → related parties and commission: allowing the automatic distribution of Commission to related parties
Tier 4 → contacting currency: by lending currency, Income based on interest
layer 5 → programmable: reserved for future realization of Turing complete programming model, so as to process blockchain data in a customized way (such as smart contract)
layer 6 → custom protocol: reserved for future use
transaction type:
abey mode allows different levels in blockchain through design, Complete a variety of transaction types. The transaction types in the second layer are as follows:
1 → fund transfer: fund transfer between accounts (1-to-1 transfer)
2 → refundable fund transfer: refundable transaction between accounts. Use escrow balance instead of regular account balance
3 → key change: change the key that can be used to process the account
4 → restore the account: recover funds from the lost and invalid account
5 → set account name: define the name of the account held by the founder
6 → sales preparation: mark the account for sale
7 → move out of the sales queue: remove the account sales mark, And the account is marked as non saleable
refundable transaction and mediator:
for the vast majority of cases, non refundable transaction is equivalent to all "pay to pay" transactions in blockchain based digital currency mode. But abey has introced the concept of refundable transactions into its digital currency model. In abey mode, the transaction marked with small flag belongs to refundable or non refundable transaction. In addition, in abey's blockchain network, each account contains two types of balance: regular and unchangeable balance (used to mark the amount that the account has received and can be paid immediately, but cannot be recovered after the payment) and escrow balance (including the transaction list marked as refundable transaction and the minutes of each transaction)
8 → payment dispute: for the corresponding transaction that has been marked as a refundable transaction, the payment dispute can be initiated only by the payer
9 → refund request: for the corresponding transaction previously marked as a refundable transaction, a refund request can be initiated, but only by the payer
10 → cancel escrow: cancel the escrow funds and return the funds to the payer immediately. It can only be initiated by the payee
11 → release trusteeship: release the trusteeship fund and add the amount to the balance of the payee's account immediately. It can only be initiated by the payer
related parties and commissions:
one of the important deficiencies in today's blockchain driven financial technology is the lack of the ability to provide rewards to related parties who sell specific procts or services. The third layer of abey blockchain can solve this problem< Lending digital currency:
lending digital currency is not only a simple and quick way to allow people to borrow legal tender, but also to ensure the security of encrypted assets. Given that today's valuable digital currencies are also used for transactions, the reason why lending digital currencies is feasible is not only that it allows borrowers to mortgage any type of cryptocurrency they save, but also that it is attractive because it is a way to retain their digital assets in a completely safe or very low-risk way. In addition, abey's model also provides built-in protection through the customer vault lending gateway (VLG), and enables the VLG to act as a buffer between the lender and the borrower
12 → borrowed funds: the borrower initiates transactions in the network, announces the intention of borrowing funds, and specifies the VLG account of the borrowed funds. The transaction is similar to depositing the balance of the regular / escrow account in the selected VLG account
13 → return of collateral: the transaction is initiated by the VLG itself. VLG will return the collateral to the borrower in accordance with the risk management policy
14 → loan repayment: the transaction is initiated by the borrower. If VLG accepts repayment of the loan in digital currency, the borrower may choose to repay the loan in digital currency. Under this condition, the digital monetary fund will be converted into VLG regular account balance<
programmable blockchain:
with its associated metadata payload, the layer of blockchain can be retained to allow the further creation of intelligent contracts between peers in the network by executing the grammar based "complete Turing basic programming language" according to the original blockchain data processing mode. For each payload, encryption or public visibility processing can be implemented, and can be performed in a dedicated virtual environment (similar to a virtual machine). This method can effectively protect data security and avoid the impact of data destruction and security vulnerabilities. The main advantage of this method is that this layer can create and enforce digital contracts without any blockchain specific programming. For Ben
The 
Ethereum mining
Berlin hard fork will mark the end of the metropolitan era. This is a key stage in Ethereum's history, which is divided into two stages (Byzantine and Constantinople), including several branches, including Atlantis, Istanbul, and finally reached its peak in Berlin
1. Pow (proof of work) workload proof
in a word: the more you do, the more you get
it relies on machines to perform mathematical operations to obtain accounting rights. Compared with other consensus mechanisms, the resource consumption is high and the supervision is weak. At the same time, the whole network needs to participate in the operation to reach a consensus every time, so the performance efficiency is relatively low. In terms of fault tolerance, 50% of nodes in the whole network are allowed to make mistakes< Advantages:
1) the algorithm is simple and easy to implement
2) there is no need to exchange additional information between nodes to reach a consensus
3) the cost of destroying the system is huge< Disadvantages:
1) waste of energy
2) it is difficult to shorten the block confirmation time
3) the new blockchain must find a different hash algorithm, otherwise it will face bitcoin attack
4) it is easy to generate bifurcation and needs to wait for multiple confirmations
5) there is no finality, and checkpoint mechanism is needed to make up for it
2. POS proof of stake
in a word: the more you hold, the more you get
the main idea is that the difficulty of obtaining the node's accounting right is inversely proportional to the equity held by the node. Compared with pow, the resource consumption brought by mathematical operation is reced to a certain extent, and the performance has also been improved correspondingly. However, it is still a way to obtain the accounting right based on hash operation competition, which is weak in supervision. The fault tolerance of the consensus mechanism is the same as pow. It is an upgrade consensus mechanism of pow, according to the proportion and time of token of each node, it can rece the difficulty of mining in equal proportion, so as to speed up the speed of finding random numbers
advantages: to a certain extent, it can shorten the time of reaching consensus; No longer need to consume a lot of energy mining
disadvantages: mining is still needed, which does not solve the pain point of commercial application in essence; All the confirmations are just a probability expression, not a certainty. Theoretically, there may be other attack effects. For example, Ethereum's Dao attack event caused Ethereum's hard fork, and etc's appearance of this event actually proved the failure of this hard fork
the principle of dpos is the same as that of POS, except that some "deputies to the National People's Congress" are selected
bitshares community first proposed dpos mechanism
the main difference from POS is that the node elects several agents, which are verified and recorded by the agents. Its compliance, performance, resource consumption and fault tolerance are similar to POS. Similar to board voting, coin holders cast a certain number of nodes to verify and account on their behalf
the working principle of dpos is:
decentralization means that each shareholder has influence according to its shareholding ratio, and the voting result of 51% shareholders will be irreversible and binding. The challenge is to achieve 51% approval in a timely and efficient way. To achieve this goal, each shareholder can delegate his voting right to a representative. The top 100 representatives with the largest number of votes will take turns to proce blocks according to the established schele. Each delegate is assigned a time period to proce the block. All representatives will receive 10% of the transaction fee equivalent to an average block. If an average block contains 100 shares as a transaction fee, a representative will receive 1 share as a reward
network delay may make some representatives fail to broadcast their blocks in time, which will lead to the bifurcation of the blockchain. However, this is unlikely to happen because the representative of the manufacturing block can establish a direct connection with the representative of the block before and after manufacturing. This direct connection to your next representative (and perhaps the next) is to make sure you get paid
this mode can generate a new block every 30 seconds, and under normal network conditions, the possibility of blockchain bifurcation is extremely small, even if it occurs, it can be solved in a few minutes
to be a delegate:
to be a delegate, you must register your public key on the network and assign it to a 32-bit unique identifier. The identifier is then referenced by the "header" of each transaction data
authorized ballot:
each wallet has a parameter setting window, in which users can select one or more representatives and grade them. Once set, each transaction made by the user will transfer the vote from "input representative" to "output representative". In general, users will not create transactions specifically for voting purposes, because that will cost them a transaction fee. But in an emergency, some users may find it worthwhile to change their vote in a more positive way by paying fees
keep representatives honest:
each wallet will display a status indicator to let users know how their representatives are doing. If they miss too many blocks, the system will recommend users to replace them with a new representative. If any representative is found to have issued an invalid block, all standard wallets will ask for a new representative to be selected before each wallet makes more transactions
resist attack:
in resisting attack, because the top 100 representatives have the same power, and each representative has an equal vote. As a result, power cannot be concentrated on a single representative by winning more than 1% of the vote. Since there are only 100 representatives, we can imagine an attacker carrying out a denial of service attack on each representative in turn. Fortunately, the threat of this particular attack can be easily mitigated by the fact that each delegate's identity is his public key rather than his IP address. This will make it more difficult to target DDoS attacks. The potential direct connection between representatives will make it more difficult to block their proction
advantages: the number of nodes participating in verification and bookkeeping is greatly reced, which can achieve second level consensus verification
disadvantages: the whole consensus mechanism still relies on token, and many commercial applications do not need token< Pbft: practical Byzantine fault tolerance
3. Pbft: practical Byzantine fault tolerance
Introction: it provides (n-1) / 3 fault tolerance on the premise of ensuring the activity and safety
in distributed computing, different computers try to reach a consensus through message exchange; But sometimes, the coordinator / commander or member / client may exchange wrong messages e to system errors, which may affect the final system consistency
the Byzantine general problem is based on the number of wrong computers to find possible solutions, which can not find an absolute answer, but can only be used to verify the effectiveness of a mechanism
the possible solutions to Byzantine problems are:
consistency is possible when n ≥ 3F + 1. Where n is the total number of computers and F is the total number of computers with problems. After the information is exchanged among computers, each computer lists all the information obtained and takes most of the results as the solution
1) the operation of the system can be separated from the existence of currency, pbft algorithm consensus that each node is composed of business participants or regulators, and the security and stability are guaranteed by business stakeholders
2) the consensus delay is about 2-5 seconds, which basically meets the requirements of commercial real-time processing
3) consensus efficiency is high, which can meet the demand of high frequency trading volume
disadvantages:
1) when 1 / 3 or more bookkeepers stop working, the system will not be able to provide services
2) when 1 / 3 or more bookkeepers work together, and all other bookkeepers are just divided into two network islands, malicious bookkeepers can make the system bifurcate, but will leave cryptographic evidence
let's talk about two domestic ones ~
4. Dbft: delegated BFT authorization Byzantine fault tolerance algorithm
Introction: dbft mechanism adopted by ant, The bookkeeper is selected by the rights and interests, and then the bookkeeper reaches a consensus through Byzantine fault-tolerant algorithm
based on pbft, this algorithm has the following improvements:
the request response mode of C / S architecture is improved to a peer-to-peer mode suitable for P2P network
the static consensus participation node is improved to a dynamic consensus participation node that can enter and exit dynamically
for the generation of consensus participation nodes, a voting mechanism based on the proportion of holding equity is designed, and the consensus participation nodes (Accounting nodes) are determined by voting
digital certificate is introced into the blockchain to solve the authentication problem of the real identity of the accounting node in voting< Advantages:
1) professional bookkeeper
2) it can tolerate any kind of errors
3) bookkeeping is completed by multiple people, and each block is final and will not be forked
4) the reliability of the algorithm has strict mathematical proof
disadvantages:
1) when 1 / 3 or more bookkeepers stop working, the system will not be able to provide services
2) when 1 / 3 or more bookkeepers commit crimes together and all other bookkeepers are divided into two network islands, malicious bookkeepers can make the system bifurcate, but leave behind cryptographic evidence
to sum up, the core of dbft mechanism is to ensure the system's finality to the maximum extent, so that the blockchain can be applied to real financial application scenarios
5. Pool verification pool
is based on traditional distributed consistency technology and data verification mechanism
advantages: it can work without token, and realizes second level consensus verification on the basis of mature distributed consistency algorithms (pasox and raft)
disadvantages: the degree of decentralization is not as good as that of bictin; It is more suitable for multi center business model.
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