Blockchain is there such a vulnerability in Ethereum?

Question

blockchain

New to blockchain. I am studying this technology. I am reading Blockchain. Application Development - Prasti Narayan.
Help understand Ethereum consensus. As far as I understood, it is necessary to solve a mathematical problem, while it can only be solved by enumeration. The response is then sent and verified. It became unclear to me if the node forms a transaction and the answer to the task is known. That is why the answer cannot be transmitted to another node, so that it would give out the answer for its own answer. Thus, he created a new block and received a reward and an emission of ether?

Answer 1

That is why the answer cannot be transmitted to another node, so that it would give out the answer for its own answer.

Maybe. It is on this principle that mining pools work.

Answer 2

Blockchain is a book about transactions, collected in such a way that in order to change old data, it would be necessary to re-assemble all subsequent transactions into blocks (the main form of attack that makes sense is to cancel your old transaction , there are others, but the main idea here is the same and the same - the blockchain must be set in stone and not change).
In PoW Consensusthe main idea is that this process of collecting a transaction into a block would be incredibly complex (all available working capacities should calculate approximately the time expected between blocks) and it is achieved in a very simple and elegant way - you need to add some nonce to the block, then take the block as a set of bytes and count its hash, then by enumeration (for this the hash must be crypto-resistant, i.e. there would be no inverse function) of this nonce number to achieve that the hash of the block begins to satisfy certain conditions (for example, the number of zeros or something else, it does not matter, the main thing is that the complexity, i.e. the average number of hash searches, can be flexibly adjusted to the current powers so that the search time is approximately necessary).
The found hash or nonce itself is not a secret, because they are only for a specific set of transactions, change the transactions and you will need to look for a new nonce.
And since the hash information from the previous block is included in the block, it means that when you try to change any old block, you will need to re-calculate the nonce for each subsequent one, because the hashes will change too.
ps Ethereum will soon move from a reliable but inconvenient pow to a vague unreliable (hard to understand 99.(9)% of the population) PoS, with which scaling is a little easier, and the emission distribution model works differently (it’s a philosophical question whether it’s good or bad). I didn’t study exactly how PoS will work on the air, the original idea of ​​​​pos is that instead of sorting through a huge number of numbers and calculations, accounts will be sorted out (the first pos coin - there were utxo transactions) and the probability of using the next one to collect a block will be equal to the sum of stake divided by all the coins in the blockchain in the stake. Pure PoS is vulnerable to transaction cancellation, since rewriting the entire blockchain does not require resources, but most of the coins in the stake are needed, and since most 'non-Bitcoin' projects are centralized from the very beginning, because their creators want a lot of money out of thin air,
History knows examples of altcoins with PoS in which the blockchain was rewritten from a very old moment (unfortunately I don’t remember the details and names), and the only way I know to solve this problem is checkpoint centralization (i.e. someone reliable will say that here this block number is the current checkpoint and nothing back, for example, in a dPoS consensus, a bunch of delegates do this at once), with all the problems that follow from this.
If they find a reliable way, then it will not be called PoS