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Author Topic: Difficulty! Do we really need it?  (Read 2172 times)
PenAndPaper
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October 15, 2014, 12:51:49 AM
 #21

Ok I do not understand it I have to admit that. Lips sealed

Just a question if you know for sure.
When calculating the total difficulty of a chain we count the values of the actual hashes or the difficulty targets in the blocks?
I 'm not sure about what you are asking... The "target" is stored into each block and that's all you need to derive the difficulty since the upper bound is well known.
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Each block is stacked on top of the previous one. Adding another block to the top makes all lower blocks more difficult to remove: there is more "weight" above each block. A transaction in a block 6 blocks deep (6 confirmations) will be very difficult to remove.
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October 15, 2014, 12:55:47 AM
 #22

This is clear and thank you for clarifying! A bit shift modifies possibility by 50%.

Yes, but the hash target doesn't necessarily move from 135 bits to 136 bits, it moves from 135.1 to 135.4.

Just a question if you know for sure. When calculating the total difficulty of a chain we count the values of the actual hashes or the difficulty targets in the blocks?

The total difficulty of a chain (for the purposes of determining which chain is longest) is the sum of the difficulty targets, and has nothing to do with the "luck" of the miners / block hashes.
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October 15, 2014, 01:22:31 AM
 #23

This is clear and thank you for clarifying! A bit shift modifies possibility by 50%.

Yes, but the hash target doesn't necessarily move from 135 bits to 136 bits, it moves from 135.1 to 135.4.

Just a question if you know for sure. When calculating the total difficulty of a chain we count the values of the actual hashes or the difficulty targets in the blocks?

The total difficulty of a chain (for the purposes of determining which chain is longest) is the sum of the difficulty targets, and has nothing to do with the "luck" of the miners / block hashes.

Thanks a lot!
Seems you have practiced a lot with difficulty and to tell you the truth my motivation was for a simpler way to model it using two numbers.
Bit transitions, dominant zeros and just pure binary operations without any large number maths involved.

PS. Was really nice sharing your opinions with me. An other interesting subject is the +2/-1 hours range for block inclusion in a chain. Does exist an alternative?    

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