In pool mining, it's my understanding that miners solve a reduced difficulty hash which proves that work is being done and also simultaneously helps solve a block.

How is this computationally possible? and how can the pool difficulty be different from the Bitcoin block? I guess I don't understand how work on blocks is computationally divided among pool miners.


2 Answers 2


From what I understand basically if the entire blockchain requires a very high hash rate (for example result should end with 100 zeros) in pool mining your shares will be based on the number of times you are able to solve a simpler problem requiring a medium hash rate (should end with 50 zeros). So you are still solving the same problem but attempts where you get the simpler answer is used to calculate the shares that you are given.

  • I don't understand how you're solving the same problem if youre looking for 2 different results. I'm starting to think that I have a misunderstanding about something more fundamental regarding how this works. Jul 16, 2017 at 17:55
  • You are still solving the same problem. For example if the problem is add a nounce to XYZ for eg. ab such that the output of the output of SHA function of that ends with 100 zeros. SHA(XYZab) is >100 zeros in the end Now suppose u keep attempting the problem with SHA(XYZcd), SHA(XYZef) and you find SHA(XYZgh) which ends with 50 zeros. That is not the correct answer but it is the answer to the same problem with a lower difficulty. If you keep posting all the combinations that gives an output of 50 zeros it proves that you are attempting to solve the problem Jul 17, 2017 at 3:51

Contrary to popular belief, mining is not something where there is progress. Each hash has the same probability of being a valid block hash. You could get lucky and find a valid hash with your next hash, or you could not. There is no progress that is made. When you mine on a lower difficulty, the target that your hash must be under is much higher than that of the networks. With enough hashes, someone will eventually find a hash that is lower than the network target, and that hash would also be lower than their pool target. The higher target (thus lower difficulty) is only for tracking who is actually doing work and how much work they are doing so that they can be paid appropriately.

  • So when mining in a pool, does it alternate algorithms? one for tracking workers and one that is actually working the blockchain? Jul 16, 2017 at 7:54
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    No. There are no different algorithms. Miners will be mining blocks for the lower difficulty, and it just so happens that due to randomness and luck, a block will be found which also matches the actual network difficulty, and that is the block that the pool submits to the network.
    – Ava Chow
    Jul 16, 2017 at 8:02
  • but isn't the difficulty of the pool a low constant number? Jul 16, 2017 at 9:05
  • Yes, but the difficulty of a block just has to be greater than or equal to the difficulty of the pool for the pool to accept the share. This means that a block can be found which has a difficulty greater than or equal to the difficulty of the network so the block would be accepted by both the pool and the network. The, difficulty of a block is not set by the miner but rather is determined by the value of the book hash itself, and the block hash is basically random.
    – Ava Chow
    Jul 16, 2017 at 9:20
  • under what conditions are the shares submitted From the pool? Jul 16, 2017 at 17:57

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