5 ms·

"It’s absurdly expensive to mine blocks to store data indefinitely." Is this true of all block chains or specific to bitcoin?

TheDong 9y ago
If you don't have mining, or a similar way to decide between various possible forks, what you have is a cryptographically secured append-only ledger (such as what the git data-format resembles). That's not a blockchain and that idea has existed for decades already. I think that idea is now being called a "blockchain" since in reality the trustless/proof-of-work nature of a true blockchain is largely wasted for specific companies.
- tscs37 9y ago
  It's a blockchain if you have a directed linked list of blocks. Even git is to some extent blockchain.
  - TheDong 9y ago
    That's a redefinition of what a blockchain is IMO. That's definitely the definition some companies are operating under.. but really? WALs and journals have existed for ages and both fit the definition of a directed list of blocks. Hell, ext2 and FAT fit that definition (inodes forming a directed list of block-references). I guess we all store our data on something that's technically a blockchain by your definition.
    - tscs37 9y ago
      It's not a redefinition, it's a definition that has been around since the 1990's [0], the only requirement for a blockchain is A) directed linked list (block points to previous block) and B) cryptographic security (use hashes as block index) Bitcoin is merely the first application to use Blockchain in a decentralized proof-of-work manner.
      - jacquesm 9y ago
        A git repository is a Merkle tree. http://en.wikipedia.org/wiki/Merkle_tree http://en.wikipedia.org/wiki/Merkle_tree A bitcoin blockchain is also a Merlke tree. But a git repository is not a blockchain.
        tscs37 9y ago
        It is a blockchain is you don't merge since you have a commit pointing at a previous commit, (block points to block), merges point to two parents but Ethereum has that almost with uncle blocks. The commit log of a repo is almost certainly a blockchain, which is why I mentioned "to some extend"
        jacquesm 9y ago
        You are simply wrong. Think of a blockchain as only one strand (say, the leftmost strand, from a leaf all the way to the root) of a Merkle tree. Think of a git repository as the whole tree. So no, they are not equivalent. If they were there would never be a way to have more than one branch depend on a previous one.
        tscs37 9y ago
        As mentioned, the git commit log, not the entire repo, which is more organized like a merkel tree, though that is only really the storage. The commit log is a strict DAG, if you don't have any merges, it is a strict blockchain, otherwise it gets fuzzy but is close enough. I never said it's equivalent but that is what a blockchain is; "A blockchain [...] is a continuously growing list of records [...] which are linked and secured using cryptography."[0] This doesn't mention "Can't be a merkle tree" for one, but also doesn't mention "can't consist of branches which merge again" or "requires proof of work" or "must use signatures" (cryptography refers to the hashes normally but can refer to anything else too) Git also acts like a blockchain, if you change the past (edit a past commit) you need to update all following commits for the new hash and their children hashes and anyone who has the repository must do a force pull, similarly to how Bitcoin rejects fork chains with less proof-of-work. It might be worth mentioning that Bitcoin also uses MerkleTrees for storage as they are very good for quickly comparing sets. A blockchain does not necessarily process financial transactions at all and I don't see why it must be a requirement. [0]: https://en.wikipedia.org/wiki/Blockchain https://en.wikipedia.org/wiki/Blockchain
deleted 9y ago
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TheDong 9y ago

If you don't have mining, or a similar way to decide between various possible forks, what you have is a cryptographically secured append-only ledger (such as what the git data-format resembles). That's not a blockchain and that idea has existed for decades already. I think that idea is now being called a "blockchain" since in reality the trustless/proof-of-work nature of a true blockchain is largely wasted for specific companies.

tscs37 9y ago
It's a blockchain if you have a directed linked list of blocks. Even git is to some extent blockchain.
- TheDong 9y ago
  That's a redefinition of what a blockchain is IMO. That's definitely the definition some companies are operating under.. but really? WALs and journals have existed for ages and both fit the definition of a directed list of blocks. Hell, ext2 and FAT fit that definition (inodes forming a directed list of block-references). I guess we all store our data on something that's technically a blockchain by your definition.
  - tscs37 9y ago
    It's not a redefinition, it's a definition that has been around since the 1990's [0], the only requirement for a blockchain is A) directed linked list (block points to previous block) and B) cryptographic security (use hashes as block index) Bitcoin is merely the first application to use Blockchain in a decentralized proof-of-work manner.
    - jacquesm 9y ago
      A git repository is a Merkle tree. http://en.wikipedia.org/wiki/Merkle_tree http://en.wikipedia.org/wiki/Merkle_tree A bitcoin blockchain is also a Merlke tree. But a git repository is not a blockchain.
      - tscs37 9y ago
        It is a blockchain is you don't merge since you have a commit pointing at a previous commit, (block points to block), merges point to two parents but Ethereum has that almost with uncle blocks. The commit log of a repo is almost certainly a blockchain, which is why I mentioned "to some extend"
        jacquesm 9y ago
        You are simply wrong. Think of a blockchain as only one strand (say, the leftmost strand, from a leaf all the way to the root) of a Merkle tree. Think of a git repository as the whole tree. So no, they are not equivalent. If they were there would never be a way to have more than one branch depend on a previous one.
        tscs37 9y ago
        As mentioned, the git commit log, not the entire repo, which is more organized like a merkel tree, though that is only really the storage. The commit log is a strict DAG, if you don't have any merges, it is a strict blockchain, otherwise it gets fuzzy but is close enough. I never said it's equivalent but that is what a blockchain is; "A blockchain [...] is a continuously growing list of records [...] which are linked and secured using cryptography."[0] This doesn't mention "Can't be a merkle tree" for one, but also doesn't mention "can't consist of branches which merge again" or "requires proof of work" or "must use signatures" (cryptography refers to the hashes normally but can refer to anything else too) Git also acts like a blockchain, if you change the past (edit a past commit) you need to update all following commits for the new hash and their children hashes and anyone who has the repository must do a force pull, similarly to how Bitcoin rejects fork chains with less proof-of-work. It might be worth mentioning that Bitcoin also uses MerkleTrees for storage as they are very good for quickly comparing sets. A blockchain does not necessarily process financial transactions at all and I don't see why it must be a requirement. [0]: https://en.wikipedia.org/wiki/Blockchain https://en.wikipedia.org/wiki/Blockchain

deleted 9y ago

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