I understand the point of mining is to decentralize away from allowing one entity to add to the ledger. What I don't understand is why it's necessary for miners to compete over who gets to add to the ledger. Why can't a random miner just be selected instantly and therefore bypass any block time? It would be just as random. What am I missing here?

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Why can't a random miner just be selected instantly and therefore bypass any block time?

The problem is: how do you select a miner in a truly random way? If the mining process was just a simple random election, who gets to enter in that lottery? How would you stop someone from just running a million fake nodes, in order to increase their chance of being selected?

These are the sort of problems that are solved by Bitcoin's proof-of-work mining. In a proof-of-work scheme, a miner must expend computational resources in order to 'enter the lottery', there are no 'free tickets', if you will.

Proof-of-work also provides a mechanism of security: in order to change the blockchain history, an attacker would need to redo all of the work from the point of change onwards. To do so, they would need more computational power than the rest of the network (51% or more). A simple 'random election' would not include this 'real world resource expenditure', or the type of security it provides.

  • A simple random number generator can make it truly random. And there are already a bunch of people running tons of nodes to increase their chances of being selected. Sure they're limited to how many due to computing power, but it doesn't matter because everyone is limited. If there was no limit, then everyone has fair chance of creating a million nodes, so it's still the same odds.
    – dcporter7
    Jan 31, 2018 at 0:02
  • After researching more last night, I believe the reason for block time is so that all miners receive the previous verified block before the next block comes in. If it was instant, people might be mining blocks without the most recent ledger and this could result in dead blocks. There needs to be time between blocks so all miner's ledgers are up to date
    – dcporter7
    Jan 31, 2018 at 0:05
  • But as far as proof-of-work goes, thats definitely a point I didn't take into consideration. That's a big aspect too! It definitely needs to be really difficult to re-mine blocks.
    – dcporter7
    Jan 31, 2018 at 0:07
  • @dcporter7 look up a ‘Sybil attack’, if mining were a random-number-generator-election, then a Sybil attack would be possible. Proof-of-work sort of creates a ‘Sybil-proof’ system. When I mentioned ‘running a million fake nodes’, this is the issue I was referencing. Running a POW miner requires resource expenditure in a way that defeats Sybil attacks, which is important in creating a fair mining protocol.
    – chytrik
    Jan 31, 2018 at 1:24

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