Protein folding isn't a good "proof of work" problem. Really the expression "proof of work" is misleading. The main point of mining is not the lottery part. The lottery is only a side effect.
The main point of mining is to extend the blockchain. Pick the last block in the blockchain, add the recent transactions and create a new block in a way that is almost imposible to forge. The blockchain keeps all the transactions without a central autority.
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Q: How are we sure that nobody replaced the old blocks with fake versions?
A: Chain the blocks, so they have to forge the old the chains of block up to the newest.
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Q: How are we sure that it's difficult to forge a lot of blocks?
A: Made it as difficult as possible, but not so difficult that it's impossible to find the next block. Pick a problem where we can predict and adjust the difficulty of the problem.
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Q: How are we sure that the blocks are legit?
A: Made it easy to verify. Finding a block should be difficult, but checking it should be easy.
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Q: How are we sure that it's really difficult to forge them?
A: Use some cryptographic secure problem (and hope that it's secure). Don't create your own apparent difficult problem.
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Q: How do we convince people to mine?
A: A lottery! Give 50 BTC for each block they found, plus fees.
The main point of mining is to extend the blockchain. Pick the last block in the blockchain, add the recent transactions and create a new block in a way that is almost imposible to forge. The blockchain keeps all the transactions without a central autority.
-
Q: How are we sure that nobody replaced the old blocks with fake versions?
A: Chain the blocks, so they have to forge the old the chains of block up to the newest.
-
Q: How are we sure that it's difficult to forge a lot of blocks?
A: Made it as difficult as possible, but not so difficult that it's impossible to find the next block. Pick a problem where we can predict and adjust the difficulty of the problem.
-
Q: How are we sure that the blocks are legit?
A: Made it easy to verify. Finding a block should be difficult, but checking it should be easy.
-
Q: How are we sure that it's really difficult to forge them?
A: Use some cryptographic secure problem (and hope that it's secure). Don't create your own apparent difficult problem.
-
Q: How do we convince people to mine?
A: A lottery! Give 50 BTC for each block they found, plus fees.