Has blockchain been attacked

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. Because each block contains its own hash value and the hash value of the previous block, changing a hash value will invalidate the rest of the blockchain
if you have problems with blockchain, you are welcome to chat in private~~~~~

3.

Recently, Vulcan team of 360 company found a series of high-risk security vulnerabilities in EOS, a blockchain platform. It is verified that some of the 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 reported this kind of vulnerability to EOS official for the first time, and assisted it to repair the security risks. The person in charge of the EOS network said that the EOS network will not be officially launched until these problems are fixed

EOS super node attack: the virtual currency transaction is completely controlled

in the attack, the attacker will construct and publish a smart contract containing malicious code, and the EOS super node will execute the malicious contract and trigger the security vulnerability. The attacker then uses the super node to pack the malicious contract into a new block, resulting in the remote control of all nodes in the network (alternative super node, exchange recharge withdrawal node, digital currency wallet server node, etc.)

because the system of the node has been completely controlled, the attacker can "do whatever he wants", such as stealing the key of the EOS super node and controlling the virtual currency transaction of the EOS network; Obtain other financial and privacy data in the participating node system of EOS network, such as digital currency in the exchange, user key stored in the wallet, key user information and privacy data, etc

What's more, an attacker can turn a node in the EOS network into a member of a botnet, launch a network attack, or become a free "miner" to extract other digital currency

source: Science and Technology News

4. When it comes to the nature of blockchain, several key words are familiar. For example, decentralization, distrust, consensus mechanism, asymmetric encryption, distributed accounting, tamper proof, absolute transparency, openness and so on. At the same time, some teaching posts also list the structure of blockchain, such as data layer, network layer, consensus layer, incentive layer, contract layer and application layer
however, it's easy for people with an eye to see why there is no security layer? In fact, several key features of blockchain have already solved the security problem. First, the blockchain uses asymmetric encryption technology. In fact, encryption and decryption are different keys, namely public key and private key. In short, the public key is open to the public, while the private key is absolutely confidential
secondly, distributed bookkeeping is a way for blockchain to store data. It can also be understood as distributed storage, which is consistent with the concept of decentralization. In the form of ledger, there is no central ledger in the network, and the ledger is stored in each node. Each node is not only independent, but also can act as the central node. Therefore, the central node will not be attacked, leading to the loss of core books or data, and the whole network will not be paralyzed
moreover, tamper proof is the basic feature of blockchain. As long as the chain can not be modified, and can not be deleted. If it needs to be changed, based on the principle of transparency and openness, the whole network and all nodes need to be informed. Therefore, under the democratic mechanism, the possibility of tampering with data at will is very low. Therefore, blockchain technology is applied in various instries, such as finance, payment, traceability, games, etc., such as the network "universe", Tencent's "come together to catch the demon", and Zhongan Huanyu blockchain "Dr dragon hunt" are the safe and high-quality procts under the blockchain technology.

5. Both indivials and enterprises can purchase alicloud servers and develop an app. However, real name authentication is required. Personal real name certification and enterprise real name certification, after passing the certification, you can easily choose cloud computing procts. Leave a message or see the content of the blog, Lao Wei has written many detailed articles, which can help you get started.

6. It is said that they made the fresh sweet scented osmanthus by themselves. They have been taught patent research for more than ten years and published papers. It is estimated that other families do not have them...

then it seems that the proct does have the flavor of sweet scented osmanthus, but it is lighter, the color is still transparent, there is no yellow or orange in imagination, and there is no petal, high technology, Don't you understand?

7.

Osmanthus fragrans doesn't belong to Osmanthus fragrans. Cigui, also known as Huaye tree, mouse thorn; It is a plant of Ilex family. Evergreen shrubs or small trees, landscaping tree species. It is mainly distributed in the middle and lower reaches of the Yangtze River in China

There are four groups of Osmanthus fragrans, namely Dangui, Jingui, Yingui and sijigui. Among them, Osmanthus fragrans, Osmanthus fragrans and Osmanthus fragrans all bloom in autumn and are collectively called August osmanthus. Generally, it takes at least 10 years for Osmanthus fragrans seedlings to bloom in open field. For newly transplanted seedlings, it is not allowed to apply fertilizer too early. Sowing seedlings, after two years of cultivation, the next spring can be transplanted, flowering period in ten years

8. In a simple explanation, 51% attack is also called majority attack. It means that malicious miners control more than 50% of the hash rate of the blockchain network, and then attack the network and take over the blockchain network, so that criminals can reverse transactions, stop payment or prevent new transactions from being confirmed
for more information about 51% attacks, you can learn about them on the password finance network,

9. How to protect my bitcoin after bifurcation
if bitcoin really forks, as an ordinary user, the biggest risk is replay attack
what is replay attack? If bitcoin is split into one or more bitcoins, such as btc1 / btc2 / btc3, each bitcoin account will have a corresponding number of all bifurcated coins according to its bitcoin balance
because the address, private key, algorithm, etc. on each chain are the same, and the transaction format is also the same, the transaction initiated on one blockchain can be broadcast on another blockchain and may be confirmed. This is the "replay attack."
in short, when you transfer btc1, your btc2 / btc3 may also be transferred at the same time
however, at present, many forked coins have done two-way anti replay attack processing to avoid the risk of replay attack after forking.

10. Hackers as long as your wallet stolen, you can use your money, do not need any cattle break means