How to store blockchain currency safely

1. 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.

2.

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 a major 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 attack successfully only when they hold more than 51% token, which is more difficult than 51% 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 greater 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 contract, and the other is to follow the principle of smart contract security development

the security development principles of smart contract are: to 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 check the hash value before installing the software to ensure that the digital wallet software has not been tampered with

The third is to use cold wallet

The fourth is to back up the private key

3. 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.

4. In 2013, vircurex, the third largest trading platform of bitcoin in the world, was attacked twice by hackers, which made vircurex fall into a serious financial crisis. As a last resort, it stopped withdrawing bitcoin, Leyte and other virtual currencies in March 2014
on the morning of February 25, 2014, Mt. GOx, the world's first exchange, stolen 744408 bitcoins in a major bitcoin theft case. According to the average price of bitcoin on the 28th day, it is equivalent to 475 million US dollars. Mt. GOx went bankrupt
on January 26, 2018, coincheck illegally removed about 260000 NEM holders at about 02:57 on that day, and then suspended some functions
on March 7, 2018, the world's second largest exchange, "coin on binance exchange". A large number of users' accounts were stolen. In the face of the hacker attack, this morning, coin an rolled back all abnormal transactions
the above lesson of xuelinlin tells us that no matter how big the exchange is, it can't guarantee the security of core assets and users' digital currency
next, I would like to say that it is safer to withdraw your digital currency to Epay blockchain wallet
Why do you say that< 1. Epay wallet adopts multiple encryption, offline cold storage
2. Bank and risk control system, anti money laundering system
3. Secured transactions are more secure, and it is the first encrypted digital wallet supporting secured transactions in the world
Epay wallet is a digital currency encrypted wallet developed by Epay global payment, and Epay global payment is the best payment channel of global cryptocurrency, The official partner of tether and the world's largest usdt charging platform account for more than 80% of the total usdt, and it is the first digital currency wallet in the world to support the top five legal currencies. Epay global payment was established in 2014 with a registered capital of 200 million yuan. Epay global payment integrates the latest blockchain technology and e-wallet to provide convenient and flexible e-payment, global bank wire transfer, payment gateway and other services for global users with a series of advantages such as diversified payment methods, low cost, high security and trust.

5. Atoken wallet is an earlier decentralized digital wallet supporting Ethereum and its smart contract token in China. Atoken wallet can store the storage and transfer of eth, and also support the storage and transfer of all tokens of Ethereum smart contract.

6. It said that you had this kind of trouble before, but I don't know when I came into contact with Wen ecology, and my world changed. Wen taught me to know blockchain, and their landing scenes, such as coinopts coin first network, their technology is also very suitable for Xiao. Find a suitable way, and you will know what you try.

7.

Bitcoin core wallet is the most complete and secure wallet on the market, and it is also the earliest bitcoin client. However, e to the huge volume of blockchain data file (blockchain) that needs to be loaded in the proct and slow startup, it will be troublesome for novices to start

bitcoin wallet

a wallet usually has multiple private keys, and many bitcoin investors also have multiple wallets. Wallets can be placed on computers and / or mobile devices, on physical storage devices, or even on paper

e-wallet - e-wallet can be downloaded software or hosted in the cloud. The former is just a format file that exists on your computer or device to facilitate transactions. Hosted (cloud based) wallets usually have a more user-friendly interface, but you will trust a third party with a private key

software Wallet - installing a wallet directly on your computer can provide you with the security of your control key. Most have relatively simple configurations and are free. The disadvantage is that they do require more maintenance in the form of backup. If your computer is stolen or damaged, and your private key is not stored elsewhere, you will lose bitcoin

Mobile Wallet - mobile wallet can be used as an application for smart phones, especially if you want to pay with bitcoin in the store or buy and sell on the road. All of the online wallets mentioned above and most of the desktop wallets have mobile versions, while others (such as Abra, airbitz and bread) are created with mobility in mind

Hardware wallets - hardware wallets are small devices that are sometimes connected to the network for bitcoin transactions. They are very secure because they are usually offline and therefore cannot be hacked. However, they may be stolen or lost along with bitcoin belonging to the stored private key. Some large investors keep their hardware wallets in secure locations, such as bank vaults. Trezor, keepkey and ledger and the case are obvious examples

paper wallets - perhaps the simplest of all wallets, these are all paper with the private key and public key of the bitcoin address printed on it. These wallets are ideal for long-term storage (obviously, away from fire and water) or as a gift of bitcoin, because they are not connected to the network, so they are more secure. However, they are more likely to be lost

with services like walletgenerator, you can easily create new addresses and print your wallet on the printer. Fold, seal, and you're done. Send some bitcoin to the address and store or distribute it safely

the Xueshuo innovation blockchain Technology Workstation of Lianqiao ecation online is the only approved "blockchain Technology Specialty" pilot workstation of "smart learning workshop 2020 Xueshuo innovation workstation" launched by the school planning, construction and development center of the Ministry of ecation of China. Based on providing diversified growth paths for students, the professional station promotes the reform of the training mode of the combination of professional degree research, proction, learning and research, and constructs the applied and compound talent training system

8. That's a fuckin 'liar. I borrowed 20000 yuan and paid it back in 36 installments. I wanted to pay more than 31000 yuan. That's usury

9. I just checked it on the Internet and said that it is the same major shareholder (Zhuo Er or something) as the P2P platform "jiashiliu" which announced the retirement of "charge and raise difference" this year.