DSA money mining

1. One of the characteristics of blockchain projects (especially public chains) is open source. Through open source code, to improve the credibility of the project, so that more people can participate. But the open source code also makes it easier for attackers to attack blockchain system. In the past two years, there have been a number of hacker attacks. Recently, the anonymous currency verge (xvg) was attacked again. The attacker locked a vulnerability in the xvg code, which allowed malicious miners to add false timestamps on the block, and then quickly dig out new blocks. In a few hours, the attacker obtained nearly $1.75 million worth of digital currency. Although the subsequent 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 other is to understand the security coding specifications and take preventive measures
the security of cryptographic algorithm
with the development of quantum computer, it will bring great security threat to the current cryptosystem. Blockchain mainly relies on elliptic curve public key encryption algorithm to generate digital signature for secure transactions. Currently, the most commonly used ECDSA, RSA, DSA, etc. can not withstand quantum attacks in theory, and there will be greater risks. More and more researchers begin to pay attention to cryptographic algorithms that can resist quantum attacks
of course, in addition to changing the algorithm, there is another way to improve the security:
refer to bitcoin's treatment of public key address to rece the potential risk of public key disclosure. As users, especially bitcoin users, 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), delegated proof of stake (dpos), practical Byzantine fault tolerance (pbft), etc
POW faces 51% attack. Because POW depends on computing power, when the attacker has the advantage of computing power, the probability of finding a new block will be greater than that of other nodes. At this time, the attacker has the ability to cancel the existing transaction. It should be noted that even in this case, the attacker can only modify his own transaction, but not the transaction of other users (the attacker does not have the private key of other users)
in POS, attackers can only attack successfully when they hold more than 51% of the token, which is more difficult than 51% of the computing power in pow
in pbft, when the malicious nodes are less than 1 / 3 of the total nodes, the system is secure. Generally speaking, any consensus mechanism has its own conditions. As an attacker, we also need to consider that once the attack is successful, the value of the system will return to zero. At this time, the attacker does not get any other valuable return except destruction
for the designers of blockchain projects, they should understand the advantages and disadvantages of each consensus mechanism, so as to select an appropriate consensus mechanism or design a new consensus mechanism according to the needs of the scene
security of smart contract
smart contract has the advantages of low operation cost and low risk of human intervention, but if there are problems in the design of smart contract, it may bring great losses. In June 2016, the Dao, the most popular funding project of Ethereum, was attacked. The hacker obtained more than 3.5 million Ethereum coins, which later led to the bifurcation of Ethereum into Eth and etc
there are two aspects of the proposed measures:
one is to audit the security of smart contracts, and the other is to follow the principles of smart contract security development
the security development principles of smart contract are: be prepared for possible errors to ensure that the code can correctly handle the bugs and vulnerabilities; Release smart contracts carefully, do well in function test and security test, and fully consider the boundary; Keep smart contracts simple; Pay attention to the threat intelligence of blockchain and check and update in time; Be clear about the characteristics of blockchain, such as calling external contracts carefully
security of digital wallet
there are three main security risks in digital wallet: first, design defects. At the end of 2014, a user lost hundreds of digital assets e to a serious random number problem (repeated r value). Second, the digital wallet contains malicious code. Third, the loss of assets caused by the loss or damage of computers and mobile phones
there are four main countermeasures:
one is to ensure the randomness of the private key
the second is to verify the hash value before software installation to ensure that the digital wallet software has not been tampered with
the third is to use cold wallets
the fourth is to back up the private key.

2. Why don't you ask your teammates? Excuse me? Generally, they get in by the card. The moment a farmer finishes building or stops building, if the side is blocked, he can go through the wall. If the construction is terminated in the process of building, he can pass

3. Steel bending machine, one of steel processing machinery. The working mechanism is a horizontal working disc rotating on the vertical axis. The steel bar is placed in the dotted line position in the figure. The supporting pin is fixed on the machine tool. The central pin and bending pin are installed on the working disc. When the disc rotates, the steel bar will be bent. In order to bend the steel bars of various diameters, there are several holes in the working plate for inserting and pressing the bending pin shaft, and the center pin shaft of different diameters can be replaced accordingly< Different types of steel bar benders have different structures:
1. Worm wheel type steel bar bender
structure: worm wheel type steel bar bender is mainly composed of family, motor, transmission system, working mechanism (working plate, insert seat, holder, rotating shaft, etc.) and control system. The walking wheel is installed under the frame, which is easy to move
2. Gear type steel bar bender
structure: the gear type steel bar bender is mainly composed of several steel bar benders, motors, gear recers, working mechanisms and electrical control systems. It changes the traditional worm gear transmission, and increases the angle automatic control mechanism and brake device
3. Steel bar hoop bending machine
structure: steel bar hoop bending machine is a special machine suitable for bending stirrups. The bending angle can be adjusted arbitrarily, and its structure is similar to that of bending machine
4. Hydraulic steel bar cutting and bending machine
structure: the hydraulic steel bar cutting and bending machine is mainly composed of hydraulic transmission system, cutting mechanism, stubborn mechanism, engine, body, etc.

4.

Inpatient social security is registered in the medical insurance ring hospitalization. When discharged, the social security card will automatically settle accounts according to the reimbursement category, and indivials need to pay the self financing part after reimbursement. That is to say, you only need to register the medical insurance according to the requirements of the hospital when you are admitted to the hospital. After successful registration, you can show the medical insurance card for medical insurance settlement when you leave the hospital

Taking Zhengzhou as an example, according to Article 41 of the notice on measures for basic medical insurance of Zhengzhou employees, the medical expenses paid by the insured personnel using their personal accounts in designated medical institutions are settled by social security card. Social insurance agencies shall settle accounts with designated medical institutions according to the actual medical expenses incurred in indivial accounts

the medical expenses of the insured in the designated medical institutions, which should be borne by the indivial, should be settled by themselves and the designated medical institutions; The part to be paid by the overall planning fund shall be accounted and settled. Social insurance agencies regularly settle medical expenses with designated medical institutions and reserve a certain proportion of quality deposit. The quality deposit shall be returned according to the annual service quality assessment results

extended information:

Article 29 of the notice on measures of basic medical insurance for employees in Zhengzhou City, if the hospitalization medical expenses that exceed the starting payment standard and do not exceed the maximum payment limit and meet the requirements, the overall planning fund shall pay according to the following proportion:

(1) the hospitalization medical expenses of in-service employees, The proportion of overall fund payment was 95% for community health service institutions, 95% for class I medical institutions, 90% for class II medical institutions and 88% for class III medical institutions

(2) for the retirees who are hospitalized, the payment proportion of the overall planning fund is 97% for the community health service institutions, 97% for the first class medical institutions, 95% for the second class medical institutions, and 93% for the third class medical institutions

the maximum annual payment limit of the fund is 150000 yuan. After the cumulative payment of the overall planning fund reaches the maximum payment limit in the natural year, the excess medical expenses shall be paid by the employees' commercial supplementary medical insurance, and the specific measures shall be implemented according to the current provisions

5. 8016's good
after opening the front, there is a big screw on the top and a connecting line baffle screw on the bottom. After unscrewing, pull out the connecting line and open the left door to extract the whole drum assembly
two spring can be seen on the right side of the mole. Take down and pull out the connecting line of the lamp. The upper part of the drum frame can be opened anticlockwise, and then it can be taken down. For the drum core, a white plug in front of the drum rotates 90 degrees and then pulls it out. Some machines have to work hard and are very tight here. The main charging rack is fixed at the back by a screw. Screw out and pull out from the rear end
the key point is that don't dirty the lamp when removing it, it will cause problems
the developing chamber should also be cleaned carefully

6. Medical insurance reimbursement principle

1. Decting the threshold fee

2. The remaining part, the part that meets the local medical insurance regulations, can be reimbursed according to the specified proportion, and the part that does not meet the local medical insurance regulations, all at their own expense

so, the actual reimbursement of your medical insurance is 1306.85, and the expense that does not meet the reimbursement is 5436.58, The part of cash payment is self-care expenses + the part that should be paid by oneself in the reimbursement part + threshold fee

7. Pay attention to the structure of the machine when dismantling the air gun. Generally, the internal components of pneumatic tools are similar, including front cover, main shaft, bearing, rotor, cam, blade, hammer block and hammer frame. When removing, pay attention to the location of some small parts, such as gasket, snap ring, rubber ring, etc. Professional maintenance of air gun or to find a professional supplier.

8.

Print the settlement form of hospitalization social security in the social security department of the hospital with the hospitalization invoice

If an indivial applies to issue a social security certificate, he / she should show his / her ID card or valid identity certificate and fill in the application form for issuance of social insurance premium payment certificate. It must be handled in person, not on behalf

1. Log in to the website of the Social Security Bureau, and after registration, you can query and print your social security statement of the previous year

2. The insured person carries the social security card to the self-service terminal to inquire about the social security payment and print the social security statement

3. Obtain the electronic statement issued by the Social Security Bureau through e-mail and print it out

extended data:

reimbursement process of medical insurance:

1. The designated medical institutions shall report the expense statement, hospitalization statement and relevant data of discharged patients in the last month to the medical insurance agency before the 10th of each month, which will be used as the basis for monthly budget and year-end final accounts after being reviewed by the medical insurance agency

2. The medical insurance agency allocates the overall expenses of hospitalization and outpatient treatment of special diseases in the previous month

3. The insured with special diseases should go to a designated medical institution designated by the labor and social security department for medical treatment and purchase, and the medical expenses incurred should be directly recorded and settled immediately