Difference between revisions of "Proof-of-X"
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== Light Clients == |
== Light Clients == |
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| + | |||
| + | Algorithm: |
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| + | * Download block headers from peers, consisting of |
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| + | ** Merkle root |
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| + | ** Hash value from previous block |
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| + | ** Nonce |
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| + | * Verify proof-of-work for each block header: hash(Merkle root, previous hash, nonce) < target (based on difficulty) |
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| + | * Consider longest chain (the one with the most work in it) as the true chain |
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| + | * To find UTXOs: |
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| + | ** (optional) Build Bloom filter for the desired transaction (a Bloom filter allows for testing set membership; it can have false positives but no false negatives) |
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| + | ** Send request to a full node: "Please give me all partial Merkle branches that match the Bloom filter for the given block" |
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| + | ** Full node sends the matching transactions and the other needed hashes from the Merkle tree (see, e.g., [http://orm-chimera-prod.s3.amazonaws.com/1234000001802/images/msbt_0705.png | Merkle tree]) |
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| + | Problem: Depends on the willingness of full nodes to provide the requested information and they don't have an incentive for doing so |
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== Advantages == |
== Advantages == |
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Revision as of 22:08, 21 November 2016
General
Goal: Secure updating of a state
Block time: trade off between time
Proof of Work
- Right to create new block: be the first to solve a puzzle based on consumption of a resource external to the system
- Miners choose one of all possible forks to contribute to (or splits among chains but with reduced efficiency per chain)
Light Clients
Algorithm:
- Download block headers from peers, consisting of
- Merkle root
- Hash value from previous block
- Nonce
- Verify proof-of-work for each block header: hash(Merkle root, previous hash, nonce) < target (based on difficulty)
- Consider longest chain (the one with the most work in it) as the true chain
- To find UTXOs:
- (optional) Build Bloom filter for the desired transaction (a Bloom filter allows for testing set membership; it can have false positives but no false negatives)
- Send request to a full node: "Please give me all partial Merkle branches that match the Bloom filter for the given block"
- Full node sends the matching transactions and the other needed hashes from the Merkle tree (see, e.g., | Merkle tree)
Problem: Depends on the willingness of full nodes to provide the requested information and they don't have an incentive for doing so
Advantages
Disadvantages
Proof of Stake
Light Clients
Advantages
Disadvantages
- Nothing at stake: Miners (voters) can vote on all forks of a blockchain
