Only one blockchain change record is possible

1.

blockchain includes public blockchain, joint (instry) blockchain and private blockchain. Public chain point-to-point e-cash system: bitcoin, smart contract and decentralized application platform: Ethereum

blockchain is a new application mode of distributed data storage, point-to-point transmission, consensus mechanism, encryption algorithm and other computer technologies

blockchain is an important concept of bitcoin. In essence, it is a decentralized database. At the same time, as the underlying technology of bitcoin, it is a series of data blocks generated by using cryptographic methods. Each data block contains a batch of bitcoin network transaction information, Used to verify the validity of its information (anti-counterfeiting) and generate the next block

extended data

according to the different degree of blockchain network centralization, three kinds of blockchains under different application scenarios are differentiated:

1. The blockchain with the whole network open and without user authorization mechanism is called public chain

2. The authorized nodes are allowed to join the network, and the information can be viewed according to the authority. It is often used in the inter agency blockchain, which is called alliance chain or instry chain

3. All the nodes in the network are in the hands of one organization, which is called private chain

alliance chain and private chain are also called licensing chain, and public chain is called non licensing chain

blockchain features

1, decentralization. Blockchain technology does not rely on additional third-party management institutions or hardware facilities, and there is no central control. In addition to the self-contained blockchain itself, each node realizes information self verification, transmission and management through distributed accounting and storage. Decentralization is the most prominent and essential feature of blockchain

2. Openness. Blockchain technology is based on open source. In addition to the private information of all parties involved in the transaction is encrypted, the data of blockchain is open to everyone. Anyone can query blockchain data and develop related applications through the open interface, so the information of the whole system is highly transparent

3. Independence. Based on consensus specifications and Protocols (similar to various mathematical algorithms such as hash algorithm used by bitcoin), the whole blockchain system does not rely on other third parties, and all nodes can automatically and safely verify and exchange data in the system without any human intervention

4. Safety. As long as 51% of all data nodes cannot be controlled, the network data cannot be arbitrarily manipulated and modified, which makes the blockchain itself relatively safe and avoids subjective and artificial data changes

5. Anonymity. Unless there are legal requirements, technically speaking, the identity information of each block node does not need to be disclosed or verified, and the information can be transferred anonymously

2. Security in blockchain comes from some attributes< Mining blocks need to use resources< Br > 2. Each block contains the hash value of the previous block< Br > imagine if the attacker wants to change the chain by changing the transaction five blocks ago. If they tamper with the block, the hash value of the block changes. Then the attacker must change the pointer from the next block to the changed block, and then change the hash value of the next block... This will continue until the end of the chain. This means that the farther the block is behind the chain, the greater the resistance to change. In fact, the attacker has to simulate the hash capability of the whole network up to the front end of the chain. However, when the attacker tries to attack, the chain continues to move forward. If the attacker's hash value is lower than the rest of the chain (< 50%), they will always chase and never proce the longest chain. Therefore, this type of blockchain can resist attacks, where the attacker's hash value is less than 50%< Br > when attackers have 51% hash value, they can rewrite the network history with a list of valid transactions. This is because they can recalculate the hash value of any block sort faster than the rest of the network, so they can ultimately guarantee a longer chain. The main danger of 51% attacks is the possibility of double spending. This simply means that an attacker can buy an item and show that they have paid with any number of confirmations on the blockchain. Once they receive the item, they can reorder the blockchain so that it doesn't include the send transaction and get a refund< Br > even if the attacker has more than 50% hash value, the attacker can only do so much damage. They can't do things like transfer money from the victim's account to their account or print more coins. This is because all transactions are recorded by the account?? Account owners sign, so even if they control the entire network, they cannot forge account signatures.

3. The information of each block in the blockchain is different, and the generation time and recorded data of each block are different. You can regard the blockchain as a bookkeeping book. Every once in a while, someone will write all the transaction information on the blockchain network to one page of the ledger, page by page, and record all the transactions on the blockchain network in turn according to the time
on the other hand, all nodes (computers in short) participating in the network will store one account book, which is updated in real time. Even if one node fails, the blockchain will not be affected.

4. Blockchain is a technical solution to collectively maintain a reliable database through centralization and distrust. This technical solution allows any number of nodes in the participating system to calculate and record all the information exchange data in the system in a period of time to a data block through cryptography algorithm, and generate the fingerprint of the data block for linking the next data block and checking. All participating nodes in the system jointly determine whether the record is true
blockchain can improve the way of data recording in audit. In the current network audit, although there is an early warning mechanism, it still needs auditors to judge and handle the abnormal records manually; Blockchain can automatically process the abnormal records through whether each node verifies and approves the block and the transaction information in it, whether the network node is attacked, and whether the account book of each node is complete, so as to make real-time audit possible. Auditors can directly access and query the effective information on the blockchain, judge whether the processing is reasonable and make corrections. In the blockchain, timestamps are used to record various transactions and operations, which can achieve historical traceability and tracking, and greatly improve the quality and efficiency of audit
blockchain can change the storage mode of audit data. In traditional audit, data are stored in an audit center server, which not only has the problems of high load and slow running speed, but also is vulnerable to attack; The blockchain audit system is a typical distributed storage, each node has the same backup, which can not only save the high cost and maintenance costs of the server, but also ensure the integrity of the data
semi public private chain can be used for audit. Blockchain can be divided into three forms: public chain, semi open private chain and full private chain. Considering the characteristics of audit instry, it is appropriate to adopt semi open private chain mode. For the audited units and enterprises, some trade secret information is not disclosed, but the pre selected nodes within the group decide the generation of the block. External suppliers can participate in the transaction but not the accounting process. Externally, it provides a third-party query node to query through the open API. In this way, it can not only ensure the internal privacy of the enterprise, but also enable the external auditors to implement real-time audit query.

5. Encryption code. Every few minutes, a new block is generated, which stores different information and consists of different passwords (double keys).

6. The solutions are as follows:
1. Regularly clean the st in the computer, turn off the computer, open the chassis, use a hair dryer and blow with cold air< At ordinary times, 360 guard, Jinshan guard and other tools should be used to clean up the system garbage and temporary files generated by the Internet, and check and kill malicious

Italian software
3. The computer configuration is poor, so try to set the virtual memory as large as possible, and install anti-virus software with less resources, such as NOD32, or only one

auxiliary anti-virus software
4. Try to set the IP to static IP, which can rece the startup time of the computer
5. Don't put too many files and icons on the computer desktop, which will slow down the reaction of the computer. Try not to install the software on disk C
6. Regularly defragment the disk. Open the drive of my computer to defragment - properties - tools

select the disk to be defragmented. Open the "disk defragmenter" window - Analysis - defragmentation - the system will start to defragment

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7. It's useless to just delete, because there is no solution to the vulnerability
the suggestion is to redo the system, and then find the guardian God to reinforce the system security for you, so as to completely plug the loopholes.

8. Not yet, you can learn Java and big data, HTML5

9. Block head, transaction details, transaction counter and block size... Are these Shenma things
blockchain is the big ledger of bitcoin network, and each block is equivalent to a page in the ledger. What information is recorded in the "account book"? At present, each block of bitcoin mainly records data such as block head, transaction details, transaction counter and block size
"block header" contains all information except transaction information, mainly including the hash value of the previous block header, which is used to ensure that blocks are connected in sequence; Time stamp: record the generation time of the block; Random number: that is, the answer to the arithmetic problem of PK for all miners in the whole network; Difficulty target: score the difficulty coefficient of the arithmetic problem
"transaction details" records in detail the transferor, income party, amount and digital signature of the transferor of each transaction, which is the main content of each block
"transaction counter" describes the number of transactions contained in each block
"block size" refers to the size of each block data. Currently, each block is limited to 1MB, which does not rule out the possibility of expansion in the future.