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Please correct me if I am wrong - but when people say private blockchain I think they mean multiple nodes that don't trust other, but not an unlimited number of

Please correct me if I am wrong - but when people say private blockchain I think they mean multiple nodes that don't trust other, but not an unlimited number of nodes or the ability for just anyone to mint coins upon it.

TheDong 8y ago
The majority of the time I see the term "private blockchain" used it's in reference to something not dissimilar to a few companies keeping an append-only ledger. In that case, each company is trusted to at least be authoritative for their entities and to be trusted to the extent that their identities are known and they may be held accountable. In that situation, an append-only log with merkle-tree-like crypto could handle the situation just fine. The key thing that isn't needed there is proof of work; participants do not need to be "rate limited" and, if a conflict arises, they can all be trusted to, say, arbitrarily pick the item with the lowest sequence number rather than needing a proof of work system. In what situations do you think a private blockchain is warranted and specifically why is proof of work necessary in that scenario?
- chrisco255 8y ago
  Blockchains have consensus built in at the protocol level. Sure, you could share an append only log, but who settles disputes? All that functionality has to move off chain, and that's a bigger risk, in my opinion.
  - TheDong 8y ago
    > Blockchains have consensus built in at the protocol level They have it built in based on picking the chain which the most work has gone into. Arbitrarily assigning a number to a transaction and having everyone to agree to pick the smallest in the case of conflict is easier and works fine if your members are all trusted to not maliciously abuse that facet of the code. Proof of work is throwing away resources to solve a problem you don't have if no one is crafting malicious transactions.
    - dboreham 8y ago
      >Arbitrarily assigning a number to a transaction and having everyone to agree to pick the smallest in the case of conflict is easier and works fine if your members are all trusted to not maliciously abuse that facet of the code. This would be like a traditional eventually consistent distributed database (using total order to resolve conflicts). And we might ask "why did those deploying private blockchains not just use that kind of thing?". I'm not sure, but potential reasons are: 1. That kind of thing doesn't actually exist in a form that they can easily use, so they re-purposed existing, reasonably proven blockchain technology to achieve an equivalent functionality. 2. The parties don't completely trust each other so in fact malicious transactions can be crafted. 3. They don't trust their software to not craft malicious trasnsactions and the blockchain provides a neat way to filter them out.
      - lalaland1125 8y ago
        Don't forget about potential reason number 4. 4. Blockchain is very hyped right now and they want to show that they are hip and cool by keeping up with the latest trends.
    - chrisco255 8y ago
      Proof of work is but one consensus algorithm. There is proof of stake, proof of authority, delegated proof of stake, etc. Dozens of different approaches out there different from Bitcoin.
- rickycook 8y ago
  but why would you? blockchain is a fine solution; why reinvent it? replace POW with POA and there are very few reasons not to use a blockchain here
  - berkes 8y ago
    Because you are literally wasting resources (PoW/PoS) to resolve conflicts that can be resolved much simpler. And to protect against sybils that cannot exist by nature of being private. Or to protect against Byzantine nodes that cannot exist by the nature of being private.

TheDong 8y ago

The majority of the time I see the term "private blockchain" used it's in reference to something not dissimilar to a few companies keeping an append-only ledger. In that case, each company is trusted to at least be authoritative for their entities and to be trusted to the extent that their identities are known and they may be held accountable. In that situation, an append-only log with merkle-tree-like crypto could handle the situation just fine. The key thing that isn't needed there is proof of work; participants do not need to be "rate limited" and, if a conflict arises, they can all be trusted to, say, arbitrarily pick the item with the lowest sequence number rather than needing a proof of work system. In what situations do you think a private blockchain is warranted and specifically why is proof of work necessary in that scenario?

chrisco255 8y ago
Blockchains have consensus built in at the protocol level. Sure, you could share an append only log, but who settles disputes? All that functionality has to move off chain, and that's a bigger risk, in my opinion.
- TheDong 8y ago
  > Blockchains have consensus built in at the protocol level They have it built in based on picking the chain which the most work has gone into. Arbitrarily assigning a number to a transaction and having everyone to agree to pick the smallest in the case of conflict is easier and works fine if your members are all trusted to not maliciously abuse that facet of the code. Proof of work is throwing away resources to solve a problem you don't have if no one is crafting malicious transactions.
  - dboreham 8y ago
    >Arbitrarily assigning a number to a transaction and having everyone to agree to pick the smallest in the case of conflict is easier and works fine if your members are all trusted to not maliciously abuse that facet of the code. This would be like a traditional eventually consistent distributed database (using total order to resolve conflicts). And we might ask "why did those deploying private blockchains not just use that kind of thing?". I'm not sure, but potential reasons are: 1. That kind of thing doesn't actually exist in a form that they can easily use, so they re-purposed existing, reasonably proven blockchain technology to achieve an equivalent functionality. 2. The parties don't completely trust each other so in fact malicious transactions can be crafted. 3. They don't trust their software to not craft malicious trasnsactions and the blockchain provides a neat way to filter them out.
    - lalaland1125 8y ago
      Don't forget about potential reason number 4. 4. Blockchain is very hyped right now and they want to show that they are hip and cool by keeping up with the latest trends.
  - chrisco255 8y ago
    Proof of work is but one consensus algorithm. There is proof of stake, proof of authority, delegated proof of stake, etc. Dozens of different approaches out there different from Bitcoin.
rickycook 8y ago
but why would you? blockchain is a fine solution; why reinvent it? replace POW with POA and there are very few reasons not to use a blockchain here
- berkes 8y ago
  Because you are literally wasting resources (PoW/PoS) to resolve conflicts that can be resolved much simpler. And to protect against sybils that cannot exist by nature of being private. Or to protect against Byzantine nodes that cannot exist by the nature of being private.