Do mining pools take any precautions to make sure that their members are not doing the exact same work (i.e. they've been given the exact same block to mine, and thus they're doing the same hash calculations as a fellow member)?


No, there's not a need. The "work" generated by the pool includes the time, transactions, transaction order, and a completely unique coinbase. All of this information is hashed once with SHA256 and then sent to the client for them to do the POW calculation on. There is absolutely no chance of two pools creating the same work, and indeed pool software is designed to make work unique to each user. Protocols like GBT and Stratum also generate work items locally so the pool server is even less involved.

  • How does the pool make the coinbase unique?
    – RentFree
    Dec 8 '13 at 23:52
  • The coinbase is largely random, it needs to be otherwise the block could contain a non-unique transaction ID, which would make the block invalid and useless. At the present time the coinbase often contains information like a vote, the name of the pool, or merged mining information. Block #212261's coinbase decodes to "#= BitMinter/P2SH/,ú¾mmÏ�|ì�i§[г\�e?3w�&ý �¶ù (¨ÇÎñÕ eu1º*" for example, which indicates the pool "bitminter" and a lot of random padding. Not all coinbases decode to human readable, a lot are just left totally random.
    – Anonymous
    Dec 8 '13 at 23:56
  • 2
    Perhap you could add to your answer how the pool software makes the work unique to each user? Dec 9 '13 at 2:28
  • This does not answer the question. You are answering the question of "how do 2 different POOLS make sure they're not doing the same work". My question was "how does an individual POOL make sure no 2 pool MEMBERS are doing the same work"
    – RentFree
    Apr 28 '14 at 15:35
  • @RentFree "and a completely unique coinbase". Jan 26 '20 at 7:58

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