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Proofs-of-WorkBitcoin: SHA-256
Compute intensiveNo value, motivates investment in SHA ASICs
Litecoin, Dogecoin: scryptMemory-access intensiveNo value, motivates investment in general-purpose computing (?)
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Can we have a proof-of-work that also produces something useful?
Challenge of Useful Proofs-of-Work
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Need to embed previous block and transactions in problemNeed random problem instances to be usefulNeed partially-selected problem instances to be hardMust be easy to verify winning resultsWant adjustable difficulty
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http://foldingcoin.net/wp/wp-content/uploads/2015/02/FoldingCoin-White-Paper-v1.0.pdf
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IEEE Security and Privacy (“Oakland”), 2014
Proof-of-Retrievability: node is storing what it should
Ensure local storage: block access depend on private key, which is also owner of coin value.