区块链卡块,区块链卡链是什么意思

近年来，随着区块链技术的不断发展，区块链卡块和区块链卡链的概念也越来越多。今天，小编就来给大家介绍一下区块链卡块和区块链卡链是什么意思。

区块链卡块是指将区块链技术应用于信用卡支付的技术。它将使用区块链技术来构建一个安全、可信赖的信用卡支付网络，从而改善传统信用卡支付的安全性、可靠性、可控性和可追溯性。它可以改善信用卡支付的效率，提高支付的安全性，减少欺诈和身份盗用的风险，并为消费者提供更多的安全保障。

区块链卡链是指将区块链技术应用于信用卡支付的供应链系统。它可以改善信用卡支付的效率，提高支付的安全性，减少欺诈和身份盗用的风险，并为消费者提供更多的安全保障。它可以更好地追踪和管理支付信息，在消费者、商家和金融机构之间构建一个安全可靠的信用卡支付网络，改善传统信用卡支付的安全性、可靠性、可控性和可追溯性。

智能合约是指使用区块链技术来创建的一种智能合同。它是一种可以实现自动执行的程序，可以自动完成支付，可以根据特定的规则自动执行合同，也可以自动完成某些任务，而无需人工干预。它可以减少信用卡支付的中间人，提高支付的安全性，减少欺诈和身份盗用的风险，并为消费者提供更多的安全保障。

以上就是关于区块链卡块、区块链卡链和智能合约的介绍，大家可以根据自己的需要选择适合自己的技术，以提高信用卡支付的安全性和可靠性。

1. Is blockchain a scam?

Blockchain technology itself is not a scam, but it does not rule out that some people use blockchain as a cover to commit scams. Several problems exist in blockchain: 1. The problem of excessive blockchain size. With the development of blockchain, the volume of blockchain data stored by nodes will become larger and larger, and the storage and computing burden will become heavier and heavier. Taking the Bitcoin blockchain as an example, the size of its complete data currently reaches about 71GB. If a user uses the Bitcoin Core client to synchronize data, it may not be possible to complete the synchronization for three days and three nights. Moreover, the data of the blockchain The volume is still increasing, which brings a great threshold to the operation of the Bitcoin Core client. 2. The problem of blockchain data confirmation time. The current blockchain system, especially the financial blockchain system, has the problem of long data confirmation time. Taking the Bitcoin blockchain as an example, the current confirmation time of a Bitcoin transaction takes about 10 minutes. In the case of 6 confirmations, you need to wait for about 1 hour. Of course, for credit card transactions, the confirmation time is 2 to 3 days. Bitcoin has made great progress, but it is still far away from the ideal state. 3. Dealing with the problem of transaction frequency The blockchain system faces the problem of too low transaction frequency. Qianyu Still taking the Bitcoin blockchain as an example, the average size of each transaction is about 250 bytes. If the block size is limited to 1MB, the number of transactions that can be accommodated is 4,000. Calculated based on the rate of generating one block every 10 minutes, 144 blocks can be generated every day, which can accommodate 576,000 transactions. Divided by the number of seconds per day, 86,400, the Bitcoin blockchain can process a maximum of 6.67 transactions per second. Currently, the actual daily transaction volume on the Bitcoin blockchain is close to the system bottleneck (picture). If the expansion problem is not resolved, it may cause congestion and delays in a large number of transactions. Average number of transactions in a Bitcoin block (Source: Block Yuan) In comparison, Paypal's overall transaction count in the third quarter of 2013 was 729 million, with an average of 93.75 transactions per second. Information from the official website of VISA, the world's largest payment card, shows that VisaNet achieved a processing capacity of 47,000 transactions per second in a 2013 test. Compared with several major payment networks such as Alipay, the Bitcoin blockchain is more like a newborn baby in terms of transaction processing frequency. Of course, this was also an early deliberate design by Satoshi Nakamoto. The Bitcoin block size was limited to 1MB to avoid the malicious behavior of rogue miners and have a negative impact on people. The reason why the Bitcoin blockchain payment network The reason why it has grown to be worth billions of dollars today lies in its decentralization. 4. The development of blockchain is restricted by the current system. On the one hand, the decentralized and autonomous characteristics of blockchain dilute the concept of national supervision and have an impact on the current system. For example, digital currencies represented by Bitcoin not only challenge the country’s right to issue currency, but also affect the transmission effect of monetary policy and weaken the central bank’s ability to regulate the economy.capabilities, leading monetary authorities to remain cautious about the development of digital currencies. On the other hand, regulatory authorities also lack full understanding and expectations of this new technology, and the establishment of laws and systems may lag behind, resulting in a lack of necessary institutional norms and legal protection for economic activities related to the use of blockchain, which inadvertently increases reduce the risks of market entities. 5. The integration cost of blockchain technology and existing systems is relatively high. For any innovation, existing institutions must ensure that it can not only create economic benefits, but also comply with regulatory requirements and connect with traditional infrastructure. Especially when deploying a new basic system, the cost of time, manpower, and material resources is very large, and the resistance encountered within existing traditional organizations is also not small. Of course, the existence of problems cannot hinder the development of blockchain. The proposal and in-depth research of technologies such as simple payment verification, side chain, and lightning network protocols have provided ideas for solving the above problems.

2. What are the disadvantages of blockchain

Blockchain has many advantages and obvious disadvantages.

1. Cannot be tampered with or revoked
This is both an advantage and a disadvantage. There is no regret medicine in the blockchain. There is almost nothing you can do about the data changes in the blockchain. This is mainly reflected in: If the transfer address If you fill it in incorrectly, it will directly cause permanent losses that cannot be reversed; if you lose the key, it will also cause permanent losses that are irreversible. In reality, if you lose your bank card or forget your password, you can still go to a bank branch and your money will still be there.

2. The transaction ledger must be made public
The blockchain is distributed. On the public chain, making a document means that everyone has a complete ledger, and due to the block Calculating balances on the chain, verifying transaction validity, etc. need to trace every account, so the transaction data is open and transparent. If I know someone's account, I can know all his wealth and every transaction. , there is no privacy at all.

3. Performance issues associated with larger data
As mentioned earlier, everyone has a complete ledger, and sometimes it is necessary to trace every record, so as time goes by , when the transaction data is very large, there will be performance problems. For example, when using it for the first time, you need to download all the transaction records in history to work properly. In order to verify that you actually have enough money for each transaction, you need to trace back the history of each transaction to calculate it. balance. Although performance problems can be alleviated through some technical means (such as indexing), the problem still clearly exists.

4. Delay of blockchain
There is delay in blockchain transactions. Taking Bitcoin as an example, the validity of the currently generated transactions is affected by network transmission, because it requires Before most nodes on the network learn about this transaction, it will have to wait until the next accounting cycle (Bitcoin controls this to about 10 minutes), that is, the transaction must be recognized by most nodes. It is also affected by a small probability event, that is, when two or more nodes compete for accounting rights on the network at the same time, then the network willTwo or more blockchain branches will be generated. At this time, which branch records the data is valid, and you have to wait for the next accounting cycle, which is ultimately determined by the longest blockchain branch. Therefore, the transaction data of the blockchain is delayed.

Blockchain, as a conceptual innovation, can have a disruptive impact in specific fields. Faced with the advantages and disadvantages of blockchain, what needs to be done is to maximize its strengths and avoid weaknesses, and make the best use of it. Therefore, whether blockchain can become the underlying technology of a new generation of financial infrastructure is still a question.

3. What happened when 360 discovered an epic vulnerability in the blockchain?

Recently, the Vulcan team of 360 Company discovered a series of high-risk security issues in the blockchain platform EOS. loopholes. It has been verified that some of these vulnerabilities can remotely execute arbitrary code on EOS nodes, that is, they can directly control and take over all nodes running on EOS through remote attacks.

In the early morning of May 29, 360 immediately reported this type of vulnerability to EOS officials and assisted them in repairing the security risks. The person in charge of the EOS network stated that the EOS network will not be officially launched until these problems are fixed.

EOS super node attack: virtual currency transactions are completely controlled

In the attack, the attacker will construct and publish a smart contract containing malicious code, EOS The super node will execute this malicious contract and trigger the security vulnerability in it. The attacker then uses the super node to package the malicious contract into a new block, which in turn causes all full nodes in the network (alternative super nodes, exchange deposit and withdrawal nodes, digital currency wallet server nodes, etc.) to be remotely controlled.

Since the attacker has completely controlled the node system, the attacker can "do whatever he wants", such as stealing the key of the EOS super node, controlling the virtual currency transactions of the EOS network; obtaining other financial information in the EOS network participating node system. and private data, such as digital currencies in exchanges, user keys stored in wallets, key user information and private data, etc.

What's more, attackers can turn nodes in the EOS network into members of the botnet, launch network attacks or become free "miners" to mine other digital currencies.

Source: Technology News

4. Bug in the Ethereum blockchain --2020/05/19

In order to prevent transaction replay, ETH (ETC) Nodes require that each transaction must have a nonce value. When each account initiates a transaction from the same node, the nonce value starts counting from 0, and sending a nonce increases by 1. The subsequent nonce will be processed only after the previous nonce is processed. Note that the prerequisite here is that the same address sends the transaction on the same node.

The following are several rules for nonce use:

● When the nonceIf it is too small (less than the nonce value used by a previous transaction), the transaction will be directly rejected.

● When the nonce is too large, the transaction will always be in the queue, which is the reason for the problem we described above;

● When sending a relatively large nonce value, and then fill in the nonce between the starting nonce and that value, then the transaction can still be executed.

● When the geth client is stopped when the transaction is in the queue, the transactions in the transaction queue will be cleared.

The first field AccountNonce, the literal translation is the account random number. It is a small but important detail in Ethereum. Ethereum creates a Nonce for each account and transaction. When a transaction is initiated from the account, the Nonce value of the current account is used as the Nonce of the transaction. Here, if it is an ordinary account, then Nonce is the number of transactions issued by it, and if it is a contract account, it is the number of contracts created from it.

Why use this Nonce? Its main purpose is to prevent repeated attacks (Replay Attack). Because transactions all need to be signed, assuming there is no Nonce, then as long as the transaction data and the initiator are determined, the signature must be the same. In this way, the attacker can regenerate an identical transaction after receiving a transaction data. And submit it again. For example, A sends a transaction to B. Because the transaction is signed, although B cannot change the transaction data, as long as he repeatedly submits the same transaction data, all the funds in the A account can be transferred to B. inside.

When using account Nonce, every time a transaction is initiated, the Nonce value of account A will increase. When B resubmits, the transaction will be rejected because the Nonce does not match. This prevents repeated attacks. Of course, the matter is not over yet, because cross-chain attacks can also be carried out. It was not until EIP-155 introduced chainID that the transaction data between different chains was incompatible. In fact, Nonce cannot really prevent repeated attacks. For example, A buys something from B, initiates transaction T1 to B, and then submits another transaction T2. ​​The gas price of T2 is higher and the priority will be prioritized. If It happens that after T2 processing is completed, the remaining funds are insufficient to pay T1, then T1 will be rejected. At this time, if B has given the thing to A, then A will have successfully attacked. Therefore, even if the transaction is processed, you still have to wait for a certain period of time to ensure that a block of sufficient depth is generated to ensure that the transaction is irreversible.

Price refers to the price per unit of Gas. The so-calledGas is the consumption of a transaction, Price is how much Ether is consumed per unit of Gas, Gas * Price is how much Ether is consumed to process a transaction, which is equivalent to the transaction fee in Bitcoin.

GasLimit limits the maximum resource consumption allowed for this transaction. In other words, transactions in Ethereum cannot consume resources without limit. This is also one of Ethereum's security strategies to prevent attacks. Those who maliciously occupy resources.

Recipient is the transaction receiver, which is a common.Address pointer type and represents an address. This value can also be empty. In this case, when the transaction is executed, an address will be created through the smart contract to complete the transaction.

Amount is the transaction amount. This is simple and requires no explanation.

Payload is more important. It is a byte array, which can be used as an instruction array to create a contract. At this time, each byte is a separate instruction; it can also be used as a data array, which is generated by the contract. instructions to operate. Contracts are created and executed by the Ethereum Virtual Machine (EVM).

V, R, and S are the signature data of the transaction. In Ethereum, after a transaction is digitally signed, the generated signature is a byte array of length 65, which is cut into three segments. The first 32 bytes are put into R, the next 32 bytes into S, and the last 1 word. Put the section into V. So why is it cut into 3 sections? Ethereum uses the ECDSA algorithm, R and S are the ECSDA signature output, and V is the Recovery ID.

R, S, V are the values ​​after the transaction is signed, which can be used to generate the signer's public key; R, S are the output values ​​of the ECDSA elliptical encryption algorithm, and V is used to restore the result

5. How to solve blockchain security issues

One of the characteristics of blockchain projects (especially public chains) is open source. Open source code improves the credibility of the project and allows more people to participate. But the openness of source code also makes it easier for attackers to attack the blockchain system. There have been many hacker attacks in the past two years. Recently, the anonymous currency Verge (XVG) has been attacked again. The attacker has locked a vulnerability in the XVG code, which allows malicious miners to add false times to blocks. After stamping, new blocks were quickly mined, and nearly US$1.75 million worth of digital currency was obtained in just a few hours. Although the attack was successfully stopped, no one can guarantee whether the attacker will attack again in the future.
Of course, blockchain developers can also take some measures
One is to use professional code audit services,
/>The second is to understand the security coding standards and nip them in the bud.
Security of cryptographic algorithms
The development of quantum computers will bring major security threats to the cryptographic systems currently used. Blockchain mainly relies on the elliptic curve public key encryption algorithm to generate digital signatures for secure transactions. Currently, the most commonly used ECDSA, RSA, DSA, etc. cannot withstand quantum attacks in theory, and there will be greater risks. More and more Researchers are beginning to focus on cryptographic algorithms that are resistant to quantum attacks.
Of course, in addition to changing the algorithm, there is another way to improve security:
Refer to Bitcoin's handling of public key addresses to reduce the potential risks caused by public key leaks. As a user, especially a Bitcoin user, the balance after each transaction is stored in a new address to ensure that the public key of the address where Bitcoin funds are stored is not leaked.
Security of consensus mechanism
The current consensus mechanisms include Proof of Work (PoW), Proof of Stake (PoS), and Delegated Proof of Stake (DPoS). , Practical Byzantine Fault Tolerance (PBFT), etc.
PoW faces 51% attack problem. Since PoW relies on computing power, when an attacker has a computing power advantage, the probability of finding a new block will be greater than that of other nodes. At this time, it has the ability to undo transactions that have already occurred. It should be noted that even in this case, the attacker can only modify his own transactions and not the transactions of other users (the attacker does not have the private keys of other users).
In PoS, an attacker can only successfully attack when he holds more than 51% of the token amount, which is more difficult than 51% of the computing power in PoW.
In PBFT, the system is safe when the malicious nodes are less than 1/3 of the total nodes. In general, any consensus mechanism has its conditions for establishment. As an attacker, you also need to consider that once the attack is successful, the value of the system will be reduced to zero. At this time, the attacker has nothing to do except destroy it. Get other valuable rewards.
For designers of blockchain projects, they should understand the advantages and disadvantages of each consensus mechanism, so as to choose an appropriate consensus mechanism or design a new consensus mechanism according to the needs of the scenario.
Security of smart contracts
Smart contracts have the advantages of low running costs and low risks of human intervention. However, if there are problems with the design of smart contracts, it may cause greater losses. In June 2016, The DAO, Ethereum's most crowdfunded project, was attacked. Hackers obtained more than 3.5 million Ethereum coins, which later caused Ethereum to fork into ETH and ETC.
The measures proposed in this regard includeTwo aspects:
The first is to conduct security audits of smart contracts,
The second is to follow the principles of smart contract security development.
The security development principles of smart contracts include: be prepared for possible errors and ensure that the code can correctly handle bugs and vulnerabilities; release smart contracts with caution, do functional testing and security testing, and fully consider boundaries; maintain The simplicity of smart contracts; pay attention to blockchain threat intelligence and check for updates in a timely manner; be clear about the characteristics of blockchain, such as cautiously calling external contracts, etc.
Security of digital wallets
Digital wallets mainly have three security risks: First, design flaws. At the end of 2014, a serious random number problem (duplication of R values) caused users to lose hundreds of digital assets in a certain lottery. Second, digital wallets contain malicious code. Third, lost assets caused by loss or damage of computers and mobile phones.
There are four main countermeasures:
The first is to ensure the randomness of the private key;
The second is to verify the hash value before installing the software to ensure that the digital wallet software has not been tampered with ;
The third is to use a cold wallet;
The fourth is to back up the private key.

6. Can blockchain freeze currency accounts?

Blockchain can freeze currency accounts.

A piece of news titled "The Central Bank Adopts a Series of Cleanup and Censorship Measures to Prevent and Resolve Financial Risks and Moral Hazards" began to circulate on major websites. The article mentioned that "Alipay has currently investigated and closed about 3,000 accounts engaged in virtual currency transactions."

A blockchain investor and currency circle boss said that it is used to trade cryptocurrencies such as Bitcoin. Multiple bank accounts of the currency have been frozen repeatedly. It can take as short as three days and as long as two months.” The direct reason why his account was frozen was that the account had been used for over-the-counter cryptocurrency trading. High Chong

“I feel that as long as it is caught trading Bitcoin (bank account) may be frozen, because some of my accounts were frozen after only being used twice, and I only traded BTC once, and the amount was only a few hundred thousand.

According to his reflection, he and many of his friends no longer use the over-the-counter trading function of the platform, and instead try their best to conduct transactions among acquaintances.

And he himself chose to stay on the sidelines because he was not optimistic about the current market situation. Only about 20% (BTC) was left, and the rest was converted into USDT or Qitan Annihilator fiat currency.

Most of the frozen accounts at the beginning of the year were suspected of suspicious transactions:

Since the beginning of this reform year, there have been frequent reports in the currency circle that trading accounts have been frozen. information. However, after later understanding, most trading accounts were frozen mainly because the accounts were suspected of suspicious transactions.

On September 13, 2017, the China Internet Finance Association (NIFA) issued the "Tips on Preventing the Risks of Bitcoin and Other So-called "Virtual Currencies"", stating that "Bitcoin and other so-called 'virtual currencies' are increasingly Become money laundering, drug trafficking, smuggling, illegal fund-raising and other illegal and criminal activities, investors should remain vigilant and report immediately if they find clues to illegal and criminal activities. ”

In early January this year, a well-known blockchain website Tieba posted a post about bank cards being frozen. It attracted a large number of onlookers, with nearly 40,000 reads and more than a hundred replies.< /p>

7. What is Blockchain

In the simplest terms, a blockchain is a distributed ledger.

Understand what this means For what it is, we first have to look at its opposite: a centralized ledger. Since blockchain technology started in finance, we will also introduce it below using banks as an example.

Here are Our process for using bank debit card transactions:

You swipe your card in a store to purchase goods.

The merchant sends a statement to your bank for the agreed amount.

Your bank verifies that you may have authorized the purchase.

The bank sends the money to the merchant.

Finally, the bank records it in its ledger This information.

There's a lot of technology involved here, but that's basically it. The last step is important - the bank records all the transactions made by the customer. This ledger goes all the way back to the first transaction the bank made .

This ledger is kept, maintained and regulated by the bank. You can read it in your online bank account but cannot change it. The bank has full control. If it decides to make changes, then There's nothing you can do.

Crucially, if hackers were able to access a bank's ledger, that could cause a lot of problems. They could change the account balance to make it look like certain transactions never happened Over, etc.

This is why distributed ledgers are so cool.

Blockchain network visualization

If banks are in distributed ledger Working on the ledger, every member of the bank will have a copy of the ledger, and whenever any member of the bank makes a purchase, they tell every other member of the bank.

Each member will verify transaction and adds it to the ledger (the added record is called a "block"). This has some important benefits, as there is no centralized authority that can manipulate the records. Hackers accessing one ledger will not be a big problem, as other ledgers The ledger can easily verify it.

On the other hand, it requires a lot of work. In short, the second system is blockchain (at least in financial scenarios).
< br />As mentioned above, the blockchain is a decentralized list of transactions. If I send Xiao Ming 2 Bitcoins, I will send a message to everyone in the network saying "I am sending Xiao Ming 2 Bitcoins", They all record transactions.

The future of blockchain, how will it change our lives?

One thing that is important about blockchain is that it is a public resource and no one really owns it because everyone owns it.

Blockchain is not just science fiction. We don’t need to understand the mechanism behind this technology, but you do need to understand that it may completely change our lives in the next 20 years.

This may sound bold, but remember, 20 years ago we were browsing the Internet on Netscape, using state-of-the-art Motorola flip phones, and buying our first DVD players. At that time, if we imagined that a computer could be held in our hands and that we could buy cars, make payments, and watch movies, it would have been considered a fantasy.

Although the impact of blockchain may not be as obvious as the Internet, nor as tangible as mobile phones, blockchain will effectively solve many worries in daily life. Such as intermediaries cheating people, transaction delays, etc. In our current lives, middlemen are everywhere and we take them for granted as a part of life. If one day these intermediaries cease to exist, you will find that the world will become a different place.

Imagine that by 2040, blockchain may become a mature and widely used technology. When one day you can't live without the blockchain just like you can't live without the Internet now, you will be surprised to find that this decentralized accounting technology has simplified the complexity and become a part of your lifestyle

8. What to do if a U.S. blockchain account is frozen

You need to check the freezing period and location through the bank where you opened your account or the bank’s telephone hotline. Contact the local police as soon as possible and ask them to provide you with the payment that led to your being implicated. If they do, provide the relevant information as requested by local police. Relevant information is generally used to explain why you transferred this fund. Therefore, generally speaking, it includes the order records of your Huobi OTC transactions within a certain period of time (you can log in to your Huobi OTC account and click the order in the upper right corner to export and print), your frozen bank card transactions, etc. In addition, if the police need you to provide personal information of a certain counterparty, please contact OTC customer service and follow the legal procedures provided by customer service.
When the above materials are provided to the police, they will give some feedback based on the different handling methods of the public security systems in various places and the different cases. For example, some will strictly require the case to be solved or withdrawn before it can be unfrozen, some can only freeze the funds involved in the case, and some places can unfreeze it directly. If the police refuse to unfreeze the funds directly after you have made the transcript, you can ask about the funds involved. If the funds involved are much smaller than the frozen funds, then you can apply to unfreeze the non-involved funds. In a legal sense, if you really did not participate in telecommunications fraud or money laundering, but were only frozen for selling digital assets, then you should be an implicated bona fide perpetrator.It is recommended to consult relevant lawyers.
Most judicial freezes are only temporarily frozen to cooperate with police investigations. They will be automatically unfrozen within two to three working days. Don't worry about this, it will be automatically unfrozen when it expires. But you should also pay attention to transferring the money during the period, because it is possible that the case involved in the case has victims in more than one place, so it may be frozen by more than one place, and it may be frozen again in the future. In addition, this 48 or 72 hours does not mean thawing on time, but may be delayed by several hours or even half a day.