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Andrew Stone
2020-10-09 13:39:42 +00:00
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protocol/blockchain/proof-of-work.md
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@@ -29,9 +29,9 @@ Though the term difficulty is often used colloquially to refer generally to the
## Chainwork ## Chainwork
Chainwork is a representation of the work performed through a block's entire history. It is calculated using the difficulties of each of the blocks in the chain. The work for a single block is calculated as <code>2<sup>256</sup> / (target + 1)</code>, or equivalently in 256-bit two's-complement arithmetic, <code>(~target / (target + 1)) + 1</code>, where `~` is the bitwise NOT operation. The chainwork for a block is the sum of its work with the work of all the blocks preceeding it. As such, when a new block is mined, its chainwork is simply its work plus the chainwork of the block before it. Chainwork is a representation of the work performed through a block's entire history. It is the [expected](https://en.wikipedia.org/wiki/Expected_value) number of hashes required to re-solve every block in the chain. It is calculated using the difficulties of each of the blocks in the chain. The work for a single block is calculated as <code>2<sup>256</sup> / (target + 1)</code>, or equivalently in 256-bit two's-complement arithmetic, <code>(~target / (target + 1)) + 1</code>, where `~` is the bitwise NOT operation. The chainwork for a block is the sum of its work with the work of all the blocks preceeding it. As such, when a new block is mined, its chainwork is simply its work plus the chainwork of the block before it.
This algorithm implies that summing chainwork makes sense. More formally, the expected number of hashes to solve one block candidate with work W is equal to the expected number of hashes to solve N block candidates with work W/N. This is proved [here](/protocol/blockchain/chainwork-proof). This algorithm implies that summing chainwork makes sense. More formally, the expected number of hashes to solve one block candidate with work W is equal to the expected number of hashes to solve N block candidates with work W/N. This, and that chainwork is the expected number of hashes, is proved [here](/protocol/blockchain/chainwork-proof).
## Extra Nonce ## Extra Nonce