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What is a blockchain consensus attack? 18183 industry channel for blockchain consensus mechanism attack

Time : 19/03/2022 Author : 249yg5 Click : + -
        Generally speaking, the common attacks against the network layer and the consensus protocol layer are denial of service (DOS) attack and witch attack (sybilattack). A denial of service attack causes a node to be unable to process normal data by sending a large number of data to the node (for example, sending a large number of small transaction requests to cause the system to be unable to process normal transactions). Witch attack is to weaken the redundant backup of correct data by controlling most nodes in the network. Generally speaking, the common attacks against the network layer and the consensus protocol layer are denial of service (DOS) attack and witch attack (sybilattack).
 
        A denial of service attack causes a node to be unable to process normal data by sending a large number of data to the node (for example, sending a large number of small transaction requests to cause the system to be unable to process normal transactions). The witch attack weakens the redundant backup of correct data by controlling most nodes in the network. In the pow consensus mechanism, miners will immediately broadcast the newly discovered blocks to the whole network. In the selfishmining attack, misbehaving miners will waste computing resources in the following ways: when they find new effective blocks, they do not immediately broadcast to the whole network, but continue to mine and try to dig more blocks before other miners dig into new blocks; When other miners dig effective blocks, the attacker will immediately broadcast the previously held effective blocks to the whole network.
 
        However, some researchers believe that it is not easy to realize this attack in practice. In the short range attack, the attacker controls a certain proportion of various resources (such as computing resources, cryptocurrency resources, etc.) to ensure the security of the system, so as to roll back the transaction (such as spending tokens or executing smart contracts) after the transaction is executed (so as to carry out the double flower attack, that is, spending a cryptocurrency multiple times). When the attacker launches a short range attack, he first submits a transaction to be rolled back to the whole network, and continues mining on the fork of the previous block (excluding the fork of the transaction to be rolled back) until the transaction gets the confirmation information of N blocks.
 
        If the number of blocks on the fork is more than N, the attacker publishes the block containing the transaction to be rolled back. Thus, since the length of the forked chain is larger than the original main chain, the nodes of the whole network regard the forked chain as the main chain. At this point, the transaction is rolled back. In the long range attack, the attacker forks the main chain of the blockchain on the historical block or even the founding block by controlling a certain proportion of system resources, in order to obtain more block rewards and / or achieve the purpose of rolling back transactions. This attack is more targeted at systems based on the consensus mechanism of proof of rights. Even though the attacker may hold only a small part of the tokens when the bifurcation occurs, he can freely trade tokens on the bifurcation, which makes it easier for the attacker to make coins and quickly form a longer blockchain.
 
        On the other hand, in a system based on the POS consensus mechanism, an attacker can use the coin age to calculate the rights and interests of nodes, and determine an effective blockchain based on the total consumed coin age. The coin age of the unused transaction output (utxo) is obtained by multiplying the coin age by the number of historical blocks before the block (such as counting coins). In the coin AGE accumulation attack, the attacker disperses the tokens held by him into different utxos and waits until his interests are far greater than the average value of the nodes. In this way, the attacker has a great possibility of continuously coining coins, so as to achieve the purpose of bifurcation of the main chain or transaction rollback (such as implementing double flower attack). In the POS consensus mechanism, solving the puzzle of the current block depends on the hash value of the previous block.
 
        An attacker with sufficient computing power and rights can interfere with the hash value of the H-th block through random trial and error method during the virtual mining process of the H-th block until the attacker can mine the H + 1-th block. This is the so-called pre computation attack. With this method, the attacker can continuously mint coins and obtain corresponding block rewards or launch a double flower attack.
 
        
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