Topic selection of blockchain security papers

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. A timestamp, usually a sequence of characters, uniquely identifies the time of a moment. Digital time stamp technology is a variant of digital signature technology. In the blockchain, timestamp means that whatever happens at a certain time will be recorded on the blockchain.

4. Search "blockchain" on HowNet to find model articles in this respect.

5. There are patches
this problem is actually very simple
your graphics card is OK! But the vertical synchronization of the graphics card is not off, so the FPS is very low. You can turn off the vertical synchronization in the properties of the graphics card
it must be this problem
the properties of the graphics card can be found by right clicking on the desktop, and then properties - Settings - Advanced<

vertical synchronization is off
in the 3D settings of the graphics card

6. It must be Tencent's security leading blockchain, which is really a good platform. At present, it has been implemented in many scenarios, such as social welfare, government data sharing and exchange, electronic access certificate, supply chain traceability, etc.

7. Security risks include three points:
loss of private key
error implementation
the protocol was attacked
at this stage, it can only be prevented, and it is unrealistic to completely solve it. After all, blockchain is just a newborn baby. Bitcoin and Ethereum are often attacked. Recently, decent, a relatively active blockchain content publishing platform, will encounter the same technical problems.