This is a really twisted take on blockchains. The whole point behind a blockchain is that cryptoeconomic incentives serve as an additional security function which is better than relying on generosity alone to contribute hashing power. So while it is true that a blockchain can exist without any kind of currency - the real genius behind blockchains is how they are designed as a new kind of corporation - one which requires no trust to pay users to create a single, shared view of an ordered list of events.
It's kind of like how in modern cryptography most of our algorithms aren't bullet proof. Cryptographers aren't saying that an algorithm can't be broken, but that it requires so much computational resources to do so that its simply improbable. We can say that blockchains also include this idea but they add the economic aspect; Now it isn't just improbable to break an algorithm (with universe sized computers) -- its also improbably (and irrationally) expensive.
Your other point is that a blockchain is simply a linked chain of documents. This is incorrect. The whole point behind a blockchain is that it serves as a way to get people to agree on an ordered list of events. The problem was never being able to form that list (anyone can hash a list of documents, its basic applied crypto.) It was getting a group of strangers to agree on a single result under highly adversarial conditions.
> The whole point behind a blockchain is that cryptoeconomic incentives serve as an additional security function which is better than relying on generosity alone to contribute hashing power.
This has nothing to do with blockchains. What you're describing is proof of work with a payout system, and you could implement that without a blockchain at all.
>So while it is true that a blockchain can exist without any kind of currency
It has always been true. This was, in fact, exclusively the case before the first cryptocurrencies - blockchains are data structures, not a concept exclusive to currency.
>Your other point is that a blockchain is simply a linked chain of documents. This is incorrect.
It is exactly correct. The use of blockchains in cryptocurrencies is irrelevant to what they are. If I build the next great money machine tomorrow using a doubly-linked list, it doesn't change what a doubly-linked list fundamentally is. The fact that many people have been introduced to the idea of a blockchain through cryptocurrencies doesn't alter the basic facts.
>The whole point behind a blockchain is that it serves as a way to get people to agree on an ordered list of events.
This is not what the blockchain does. The blockchain helps to ensure that Proof of Work is effective for maintaining consensus after blocks are made - it's the role of PoW to produce the agreement. A blockchain without PoW would allow members to produce new combinations of blocks at will to edit the history.
Okay, lets argue that a blockchain is simply a data structure to create a linked list of hashes... Do you know what's part of that data structure as defined in the original paper: the format of a new block hash (how many zeros it has.) It's the fingerprint of a block that decides how to extend the chain. So if you simply decide to build a linked chain of blocks without any regard to the format of block hashes (proof-of-work) and the total accumulative hashing power, then it makes no sense at all.
Like I said: you can't just abstract this part away as a "data structure" and still have it mean anything. Without proof-of-work your toy example is literally just a made-up document sitting on a single computer.
>blockchains are data structures, not a concept exclusive to currency.
Blockchains as a linked list of hashes don't make sense. You need proof-of-work to decide on the chain. Proof-of-work is expensive so without the currency, proof-of-work doesn't make sense. There are other ways to agree on the order of events but they are not blockchains as understood by the experts in this space (and removing any one of these things undermines the benefits.)
Journalists and enterprise "blockchains" enthusiasts are free to use the term however they like but it doesn't change the fact that blockchains were introduced as an incentivized, trust-free ledger of value -- and by removing any one of its parts the benefits are still lost.
>This is not what the blockchain does. The blockchain helps to ensure that Proof of Work is effective for maintaining consensus after blocks are made - it's the role of PoW to produce the agreement. A blockchain without PoW would allow members to produce new combinations of blocks at will to edit the history.
Blockchains use proof-of-work to create agreement and pay anonymous contributors for doing the work to do so, its as simple as that. A "blockchain" without either of these things is not a blockchain. Incentives are needed to improve social scalability and ensure that there is a reason to continue to secure the ledger.
Proof-of-work is used to give the chain its meaning. I could hash a list of documents right now that said I had millions of dollars but this list couldn't be used by anyone else in an untrusting network of computers without a consensus algorithm... It just so happens that proof-of-work is still the most secure way to do that consensus. So you cannot abstract it away as a "data structure" independent from proof-of-work and the incentives that drive it...
The argument you're trying to make about "blockchains" is something I've only seen enterprise blockchain enthusiasts make about ledgers, and these people usually don't understand the system very well so they end up taking parts of the blockchain away and building something that makes little sense in the end (sometimes its an improvement but usually not.)
It's kind of like how in modern cryptography most of our algorithms aren't bullet proof. Cryptographers aren't saying that an algorithm can't be broken, but that it requires so much computational resources to do so that its simply improbable. We can say that blockchains also include this idea but they add the economic aspect; Now it isn't just improbable to break an algorithm (with universe sized computers) -- its also improbably (and irrationally) expensive.
Your other point is that a blockchain is simply a linked chain of documents. This is incorrect. The whole point behind a blockchain is that it serves as a way to get people to agree on an ordered list of events. The problem was never being able to form that list (anyone can hash a list of documents, its basic applied crypto.) It was getting a group of strangers to agree on a single result under highly adversarial conditions.
See also: http://unenumerated.blogspot.com.au/2017/02/money-blockchain...