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Since my following quesiton is quite similar to this one Why is mining necessary for the Bitcoin network/system? I'm referring to the mentioned points of the accepted answer of this question that does in my opinion not answer the question at all or quite consice even though the answer is very long it just does not refer to the question. I'll explain why I make that statement.
Fairness - No massive energy consuming process is required (mining) ==> Does not answer the why mining
Stability - He also does not answer the why question he just assumes it is neccessary and explains the why a tranaction os not irreversible process in more detail. But he does not answer the why mining is required question, again he just assumes it is required and then explains a process built on that assumption.
Safety and security - At the last paragraph of this he comes up with a reason. The 51% attack. Is this the only reason that mining is required?
I'll also ask the question again: We could just hash the block without a nonce and it is also checksummed and the data integrity is ensured just as well as with a nonce. So why we need the nonce that requires such a massive energy consuming process? Is it only avoid avoid a 51% attack?
It seems to me that your questions are answered in these two related topics: Is there a way to set up proof-of-work systems so they would be even more useful?, What exactly is Mining?
– Murch – 2017-06-19T21:04:20.017Can you explain exactly what you're proposing? If I have 10 bitcoins and I produce two transactions, one sending them to address A and one sending them to address B, how do you ensure we all agree which one of those two is valid? And without such a mechanism, how can anyone ever be sure they can form a transaction others will accept as valid? PoW was the first solution to the double spend problem that didn't require a central authority. There are now others, but it's a hard problem that won't solve itself by magic. – David Schwartz – 2017-06-19T22:37:34.293