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Author Topic: Strong solution, weak solution - orphanned block process  (Read 1211 times)
marcus_of_augustus
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May 31, 2011, 09:08:39 AM
 #1

Just wondering if there is an opening for the following type of questionable behaviour on the network.

A large miner with an incentive to collect as many solution blocks as possible has a program running to filter their block solutions outputs.

A weak solution is broadcast immediately to the network to earn the rewards, however if a sufficiently strong solution is found it is withheld until a competing node broadcasts an inferior solution. At this point, the miner then broadcasts their strong solution confident it will be accepted across the network and the weaker competing solution will be orphaned.

In this way, the large miner is effectively reducing the power of the competition on the rest of the network and thus keeping more of the rewards for themselves. Anything to stop this?

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Pieter Wuille
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May 31, 2011, 09:15:24 AM
 #2

Blocks count proportional to their difficulty, i.e. the fraction of the target they had to beat - not the actual fraction of it they reached.

There is no way to have a better solution for a given block when one is already created, as the difficulty is fixed.

Only when doing a multi-block attack crossing a retarget boundary (height multiple of 2016), one can influence the effect of the retarget, and thereby the difficulty.

aka sipa, core dev team

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marcus_of_augustus
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May 31, 2011, 09:19:15 AM
 #3

Blocks count proportional to their difficulty, i.e. the fraction of the target they had to beat - not the actual fraction of it they reached.

There is no way to have a better solution for a given block when one is already created, as the difficulty is fixed.

Only when doing a multi-block attack crossing a retarget boundary (height multiple of 2016), one can influence the effect of the retarget, and thereby the difficulty.

Hmmm, okay I must not understand the orphanning process can you elaborate on that?

 How does a block get orphaned if there is no such thing as a "better" solution?

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May 31, 2011, 09:24:54 AM
 #4

When two successor blocks B1 and B2 are generated simultaneously for a single block A, part of the network will receive B1 first, and another part B2. Both will assume the one they saw first will win, and work with that. However, if B1 is extended first with a successor block C, while B2 isn't extended yet, all nodes that were working with B2 will realize the chain containing B1 is better now (as it longer, not because they individual blocks in it are better), and switch to A->B1->C as best chain.

aka sipa, core dev team

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marcus_of_augustus
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May 31, 2011, 09:28:05 AM
 #5

When two successor blocks B1 and B2 are generated simultaneously for a single block A, part of the network will receive B1 first, and another part B2. Both will assume the one they saw first will win, and work with that. However, if B1 is extended first with a successor block C, while B2 isn't extended yet, all nodes that were working with B2 will realize the chain containing B1 is better now (as it longer, not because they individual blocks in it are better), and switch to A->B1->C as best chain.

Ah, thanks.

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