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Comment by bizzleDawg | Hacker News Reader

Something that confuses me about this blockchain hype. I was under the impression that it's the distributed nature of crypyo-currencies that makes them secure as opposed to the blockchain alone? It doesn't seem like it would be that hard to re-calculate >1M sha256's to rewrite the chain if it's all a system owned/controlled by one company. Am i missing the point?

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Yeah,you also need enough people willing to mine (and spend a lot of money doing so) your pork chops blockchain, otherwise anyone could come along and do a 50% attack.

Yeah. Isn't this a major problem with all of these alternative implementations? The 50% problem will always be an issues in small deployments.

It's still a problem in the largest deployment. Does anyone have a "solution" to this?

In this specific case, it seems like what they really should do is have a set of trusted nodes for ledger replication.

Surely the best antidote to the 51% attack is to have a large population of nodes so that an attack would have to be prohibitively large?

W.r.t. having a set of trusted nodes, that's fine, however does the blockchain add anything in this situation?

No. That's actually my point. This industry probably doesn't want to invest in always having 51% of the nodes, so trusted central ledgers makes more sense to me.

The solution is to not use PoW.

Private chains don't depend on PoW.

Isn't PoW the defining characteristic of a blockchain?

No, it is just a good(the best?) way to do public blockchains.

Just to give a bit more detail with a blockchain you need some way to limit who can create a new block since you can change history by building a chain on an earlier block if you can create as many blocks as you want. In public networks this is hard since people can create as MD Danny accounts as they want so PoW which limits who can submit by resource usage or something similar is needed. In a private network you know all the participants so you can achieve the same result with something as simple as round robin.

To me that feels like just a general consensus database problem, which has been solved a long time before bitcoin came along and "blockchain" gained mindshare. It appears "private blockchain" is mostly trying to ride the buzzword hype if it doesn't incorporate the new ideas and solutions that Satoshi presented, which is mostly about generating consensus for a ledger among a set of anonymous and possibly hostile peer-to-peer nodes on a public network?

Right so it's just a different way to solve the problem.

Satoshi didn't coin the term blockchain and they existed for a long time before bitcoin so giving him sole claim to it because it paired it with a feature that isn't specifically required to have a blockchain seems silly.

That said I do agree that their are a lot of buzzword vultures using it at the moment for stupid business ideas though I think 99% of the bitcoin business ideas are poorly thought out and poor replacements for existing solutions("but with bitcoin!") so it's no surprise 99% of the blockchain ones are too.

You can do Proof of Authority instead of Proof of Work to cut down costs.

The real reason behind techniques such as PoW instead of just Distributed Byzantine Fault Tolerance algorithms is scaling in terms of number of validators. Most of DBFTs (afaik Algorand is the only exception) don't really scale. Proof of Authority behaves similarly to PoW, since it also does not have that problem.

Go with DBFT unless you want to have huge number of validators.

That's a valid point. I suppose the whole blockchain idea has several modular interchangeable parts though, including deciding what chain is authoritative, who can mine a block, and so on.

In the original form though, it makes no sense to fire up your own bitcoin, because when it's small it's vulnerable to the attack you mention.

There are different ways to limit who can write to a chain at the current time to reduce overhead. PoW is just the most popular(are arguably the best for public chains). Private chains don't need that since you know all the participants you can do something as simple as round robin.

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